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zc.buildout 1.0.0b30

System for managing development buildouts

Latest Version: 2.5.3

Contents

The Buildout project provides support for creating applications, especially Python applications. It provides tools for assembling applications from multiple parts, Python or otherwise. An application may actually contain multiple programs, processes, and configuration settings.

The word “buildout” refers to a description of a set of parts and the software to create and assemble them. It is often used informally to refer to an installed system based on a buildout definition. For example, if we are creating an application named “Foo”, then “the Foo buildout” is the collection of configuration and application-specific software that allows an instance of the application to be created. We may refer to such an instance of the application informally as “a Foo buildout”.

To get a feel for some of the things you might use buildouts for, see the Buildout examples.

To lean more about using buildouts, see Detailed Documentation.

Recipes

Existing recipes include:

zc.recipe.egg
The egg recipe installes one or more eggs, with their dependencies. It installs their console-script entry points with the needed eggs included in their paths.
zc.recipe.testrunner
The testrunner egg installs creates a test runner script for one or more eggs.
zc.recipe.zope3checkout
The zope3checkout recipe installs a Zope 3 checkout into a buildout.
zc.recipe.zope3instance
The zope3instance recipe sets up a Zope 3 instance.
zc.recipe.filestorage
The filestorage recipe sets up a ZODB file storage for use in a Zope 3 instance creayed by the zope3instance recipe.

Buildout examples

Here are a few examples of what you can do with buildouts. We’ll present these as a set of use cases.

Try out an egg

Sometimes you want to try an egg (or eggs) that someone has released. You’d like to get a Python interpreter that lets you try things interactively or run sample scripts without having to do path manipulations. If you can and don’t mind modifying your Python installation, you could use easy_install, otherwise, you could create a directory somewhere and create a buildout.cfg file in that directory containing:

[buildout]
parts = mypython

[mypython]
recipe = zc.recipe.egg
interpreter = mypython
eggs = theegg

where theegg is the name of the egg you want to try out.

Run buildout in this directory. It will create a bin subdirectory that includes a mypython script. If you run mypython without any arguments you’ll get an interactive interpreter with the egg in the path. If you run it with a script and script arguments, the script will run with the egg in its path. Of course, you can specify as many eggs as you want in the eggs option.

If the egg provides any scripts (console_scripts entry points), those will be installed in your bin directory too.

Work on a package

I often work on packages that are managed separately. They don’t have scripts to be installed, but I want to be able to run their tests using the zope.testing test runner. In this kind of application, the program to be installed is the test runner. A good example of this is zc.ngi.

Here I have a subversion project for the zc.ngi package. The software is in the src directory. The configuration file is very simple:

[buildout]
develop = .
parts = test

[test]
recipe = zc.recipe.testrunner
eggs = zc.ngi

I use the develop option to create a develop egg based on the current directory. I request a test script named “test” using the zc.recipe.testrunner recipe. In the section for the test script, I specify that I want to run the tests in the zc.ngi package.

When I check out this project into a new sandbox, I run bootstrap.py to get setuptools and zc.buildout and create bin/buildout. I run bin/buildout, which installs the test script, bin/test, which I can then use to run the tests.

This is probably the most common type of buildout.

The zc.buildout project is a slightly more complex example of this type of buildout.

Install egg-based scripts

A variation of the Try out an egg use case is to install scripts into your ~/bin directory (on Unix, of course). My ~/bin directory is a buildout with a configuration file that looks like:

[buildout]
parts = foo bar
bin-directory = .

[foo]
...

whwre foo and bar are packages with scripts that I want available. As I need new scripts, I can add additional sections. The bin-directory option specified that scripts should be installed into the current directory.

Multi-program multi-machine systems

Using an older prototype version of the buildout, we’ve build a number of systems involving multiple programs, databases, and machines. One typical example consists of:

  • Multiple Zope instances
  • Multiple ZEO servers
  • An LDAP server
  • Cache-invalidation and Mail delivery servers
  • Dozens of add-on packages
  • Multiple test runners
  • Multiple deployment modes, including dev, stage, and prod, with prod deployment over multiple servers

Parts installed include:

  • Application software installs, including Zope, ZEO and LDAP software
  • Add-on packages
  • Bundles of configuration that define Zope, ZEO and LDAP instances
  • Utility scripts such as test runners, server-control scripts, cron jobs.

Questions and Bug Reporting

Please send questions and comments to the distutils SIG mailing list.

Report bugs using the zc.buildout Launchpad Bug Tracker.

Status

The buildout system is under active development. Some near-term priorities include:

  • Fixing bugs
  • Adding support for making distributions from buildouts

Change History

1.0.0b30 (2007-08-20)

Feature Changes

  • Changed the default policy back to what it was to avoid breakage in existing buildouts. Use:

    [buildout]
    prefer-final = true
    

    to get the new policy. The new policy will go into effect in buildout 2.

1.0.0b29 (2007-08-20)

Feature Changes

  • Now, final distributions are prefered over non-final versions. If both final and non-final versions satisfy a requirement, then the final version will be used even if it is older. The normal way to override this for specific packages is to specifically require a non-final version, either specifically or via a lower bound.

  • There is a buildout prefer-final version that can be used with a value of “false”:

    prefer-final = false
    

    To prefer newer versions, regardless of whether or not they are final, buildout-wide.

  • The new simple Python index, http://cheeseshop.python.org/simple, is used as the default index. This will provide better performance than the human package index interface, http://pypi.python.org/pypi. More importantly, it lists hidden distributions, so buildouts with fixed distribution versions will be able to find old distributions even if the distributions have been hidden in the human PyPI interface.

Bugs Fixed

  • 126441: Look for default.cfg in the right place on Windows.

1.0.0b28 (2007-07-05)

Bugs Fixed

  • When requiring a specific version, buildout looked for new versions even if that single version was already installed.

1.0.0b27 (2007-06-20)

Bugs Fixed

  • Scripts were generated incorrectly on Windows. This included the buildout script itself, making buildout completely unusable.

1.0.0b26 (2007-06-19)

Feature Changes

  • Thanks to recent fixes in setuptools, I was able to change buildout to use find-link and index information when searching extensions.

    Sadly, this work, especially the timing, was motivated my the need to use alternate indexes due to performance problems in the cheese shop (http://www.python.org/pypi/). I really home we can address these performance problems soon.

1.0.0b25 (2007-05-31)

Feature Changes

  • buildout now changes to the buildout directory before running recipe install and update methods.
  • Added a new init command for creating a new buildout. This creates an empty configuration file and then bootstraps.
  • Except when using the new init command, it is now an error to run buildout without a configuration file.
  • In verbose mode, when adding distributions to fulful requirements of already-added distributions, we now show why the new distributions are being added.
  • Changed the logging format to exclude the logger name for the zc.buildout logger. This reduces noise in the output.
  • Clean up lots of messages, adding missing periods and adding quotes around requirement strings and file paths.

Bugs Fixed

  • 114614: Buildouts could take a very long time if there were dependency problems in large sets of pathologically interdependent packages.

  • 59270: Buggy recipes can cause failures in later recipes via chdir

  • 61890: file:// urls don’t seem to work in find-links

    setuptools requires that file urls that point to directories must end in a “/”. Added a workaround.

  • 75607: buildout should not run if it creates an empty buildout.cfg

1.0.0b24 (2007-05-09)

Feature Changes

  • Improved error reporting by showing which packages require other packages that can’t be found or that cause version conflicts.
  • Added an API for use by recipe writers to clean up created files when recipe errors occur.
  • Log installed scripts.

Bugs Fixed

  • 92891: bootstrap crashes with recipe option in buildout section.
  • 113085: Buildout exited with a zero exist status when internal errors occured.

1.0.0b23 (2007-03-19)

Feature Changes

  • Added support for download caches. A buildout can specify a cache for distribution downloads. The cache can be shared among buildouts to reduce network access and to support creating source distributions for applications allowing install without network access.
  • Log scripts created, as suggested in: https://bugs.launchpad.net/zc.buildout/+bug/71353

Bugs Fixed

  • It wasn’t possible to give options on the command line for sections not defined in a configuration file.

1.0.0b22 (2007-03-15)

Feature Changes

  • Improved error reporting and debugging support:
    • Added “logical tracebacks” that show functionally what the buildout was doing when an error occurs. Don’t show a Python traceback unless the -D option is used.
    • Added a -D option that causes the buildout to print a traceback and start the pdb post-mortem debugger when an error occurs.
    • Warnings are printed for unused options in the buildout section and installed-part sections. This should make it easier to catch option misspellings.
  • Changed the way the installed database (.installed.cfg) is handled to avoid database corruption when a user breaks out of a buildout with control-c.
  • Don’t save an installed database if there are no installed parts or develop egg links.

1.0.0b21 (2007-03-06)

Feature Changes

  • Added support for repeatable buildouts by allowing egg versions to be specified in a versions section.

  • The easy_install module install and build functions now accept a versions argument that supplied to mapping from project name to version numbers. This can be used to fix version numbers for required distributions and their depenencies.

    When a version isn’t fixed, using either a versions option or using a fixed version number in a requirement, then a debug log message is emitted indicating the version picked. This is useful for setting versions options.

    A default_versions function can be used to set a default value for this option.

  • Adjusted the output for verbosity levels. Using a single -v option no longer causes voluminous setuptools output. Uisng -vv and -vvv now triggers extra setuptools output.

  • Added a remove testing helper function that removes files or directories.

1.0.0b20 (2007-02-08)

Feature Changes

  • Added a buildout newest option, to control whether the newest distributions should be sought to meet requirements. This might also provide a hint to recipes that don’t deal with distributions. For example, a recipe that manages subversion checkouts might not update a checkout if newest is set to “false”.

  • Added a newest keyword parameter to the zc.buildout.easy_install.install and zc.buildout.easy_install.build functions to control whether the newest distributions that meed given requirements should be sought. If a false value is provided for this parameter and already installed eggs meet the given requirements, then no attempt will be made to search for newer distributions.

  • The recipe-testing support setUp function now adds the name buildout to the test namespace with a value that is the path to the buildout script in the sample buildout. This allows tests to use

    >>> print system(buildout),
    

    rather than:

    >>> print system(join('bin', 'buildout')),
    

Bugs Fixed

  • Paths returned from update methods replaced lists of installed files rather than augmenting them.

1.0.0b19 (2007-01-24)

Bugs Fixed

  • Explicitly specifying a Python executable failed if the output of running Python with the -V option included a 2-digit (rather than a 3-digit) version number.

1.0.0b18 (2007-01-22)

Feature Changes

  • Added documentation for some previously undocumented features of the easy_install APIs.
  • By popular demand, added a -o command-line option that is a short hand for the assignment buildout:offline=true.

Bugs Fixed

  • When deciding whether recipe develop eggs had changed, buildout incorrectly considered files in .svn and CVS directories.

1.0.0b17 (2006-12-07)

Feature Changes

  • Configuration files can now be loaded from URLs.

Bugs Fixed

1.0.0b16 (2006-12-07)

Feature Changes

  • A new command-line argument, -U, suppresses reading user defaults.
  • You can now suppress use of an installed-part database (e.g. .installed.cfg) by sprifying an empty value for the buildout installed option.

Bugs Fixed

  • When the install command is used with a list of parts, only those parts are supposed to be installed, but the buildout was also building parts that those parts depended on.

1.0.0b15 (2006-12-06)

Bugs Fixed

  • Uninstall recipes weren’t loaded correctly in cases where no parts in the (new) configuration used the recipe egg.

1.0.0b14 (2006-12-05)

Feature Changes

  • Added uninstall recipes for dealing with complex uninstallation scenarios.

Bugs Fixed

  • Automatic upgrades weren’t performed on Windows due to a bug that caused buildout to incorrectly determine that it wasn’t running locally in a buildout.
  • Fixed some spurious test failures on Windows.

1.0.0b13 (2006-12-04)

Feature Changes

  • Variable substitutions now reflect option data written by recipes.
  • A part referenced by a part in a parts list is now added to the parts list before the referencing part. This means that you can omit parts from the parts list if they are referenced by other parts.
  • Added a develop function to the easy_install module to aid in creating develop eggs with custom build_ext options.
  • The build and develop functions in the easy_install module now return the path of the egg or egg link created.
  • Removed the limitation that parts named in the install command can only name configured parts.
  • Removed support ConfigParser-style variable substitutions (e.g. %(foo)s). Only the string-template style of variable (e.g. ${section:option}) substitutions will be supported. Supporting both violates “there’s only one way to do it”.
  • Deprecated the buildout-section extendedBy option.

Bugs Fixed

  • We treat setuptools as a dependency of any distribution that (declares that it) uses namespace packages, whether it declares setuptools as a dependency or not. This wasn’t working for eggs intalled by virtue of being dependencies.

1.0.0b12 (2006-10-24)

Feature Changes

  • Added an initialization argument to the zc.buildout.easy_install.scripts function to include initialization code in generated scripts.

1.0.0b11 (2006-10-24)

Bugs Fixed

67737
Verbose and quite output options caused errors when the develop buildout option was used to create develop eggs.
67871
Installation failed if the source was a (local) unzipped egg.
67873
There was an error in producing an error message when part names passed to the install command weren’t included in the configuration.

1.0.0b10 (2006-10-16)

Feature Changes

  • Renamed the runsetup command to setup. (The old name still works.)
  • Added a recipe update method. Now install is only called when a part is installed for the first time, or after an uninstall. Otherwise, update is called. For backward compatibility, recipes that don’t define update methiods are still supported.
  • If a distribution defines namespace packages but fails to declare setuptools as one of its dependencies, we now treat setuptools as an implicit dependency. We generate a warning if the distribution is a develop egg.
  • You can now create develop eggs for setup scripts that don’t use setuptools.

Bugs Fixed

  • Egg links weren’t removed when corresponding entries were removed from develop sections.
  • Running a non-local buildout command (one not installed in the buildout) ket to a hang if there were new versions of zc.buildout or setuptools were available. Now we issue a warning and don’t upgrade.
  • When installing zip-safe eggs from local directories, the eggs were moved, rather than copied, removing them from the source directory.

1.0.0b9 (2006-10-02)

Bugs Fixed

Non-zip-safe eggs were not unzipped when they were installed.

1.0.0b8 (2006-10-01)

Bugs Fixed

  • Installing source distributions failed when using alternate Python versions (depending on the versions of Python used.)
  • Installing eggs wasn’t handled as efficiently as possible due to a bug in egg URL parsing.
  • Fixed a bug in runsetup that caused setup scripts that introspected __file__ to fail.

1.0.0b7

Added a documented testing framework for use by recipes. Refactored the buildout tests to use it.

Added a runsetup command run a setup script. This is handy if, like me, you don’t install setuptools in your system Python.

1.0.0b6

Fixed https://launchpad.net/products/zc.buildout/+bug/60582 Use of extension options caused bootstrapping to fail if the eggs directory didn’t already exist. We no longer use extensions for bootstrapping. There really isn’t any reason to anyway.

1.0.0b5

Refactored to do more work in buildout and less work in easy_install. This makes things go a little faster, makes errors a little easier to handle, and allows extensions (like the sftp extension) to influence more of the process. This was done to fix a problem in using the sftp support.

1.0.0b4

  • Added an experimental extensions mechanism, mainly to support adding sftp support to buildouts that need it.
  • Fixed buildout self-updating on Windows.

1.0.0b3

  • Added a help option (-h, –help)

  • Increased the default level of verbosity.

  • Buildouts now automatically update themselves to new versions of zc.buildout and setuptools.

  • Added Windows support.

  • Added a recipe API for generating user errors.

  • No-longer generate a py_zc.buildout script.

  • Fixed some bugs in variable substitutions.

    The characters “-“, “.” and ” “, weren’t allowed in section or option names.

    Substitutions with invalid names were ignored, which caused missleading failures downstream.

  • Improved error handling. No longer show tracebacks for user errors.

  • Now require a recipe option (and therefore a section) for every part.

  • Expanded the easy_install module API to:

    • Allow extra paths to be provided
    • Specify explicit entry points
    • Specify entry-point arguments

1.0.0b2

Added support for specifying some build_ext options when installing eggs from source distributions.

1.0.0b1

  • Changed the bootstrapping code to only install setuptools and zc.buildout. The bootstrap code no-longer runs the buildout itself. This was to fix a bug that caused parts to be recreated unnecessarily because the recipe signature in the initial buildout reflected temporary locations for setuptools and zc.buildout.
  • Now create a minimal setup.py if it doesn’t exist and issue a warning that it is being created.
  • Fixed bug in saving installed configuration data. %’s and extra spaces weren’t quoted.

1.0.0a1

Initial public version

Detailed Documentation

Buildouts

The word “buildout” refers to a description of a set of parts and the software to create and assemble them. It is often used informally to refer to an installed system based on a buildout definition. For example, if we are creating an application named “Foo”, then “the Foo buildout” is the collection of configuration and application-specific software that allows an instance of the application to be created. We may refer to such an instance of the application informally as “a Foo buildout”.

This document describes how to define buildouts using buildout configuration files and recipes. There are three ways to set up the buildout software and create a buildout instance:

  1. Install the zc.buildout egg with easy_install and use the buildout script installed in a Python scripts area.
  2. Use the buildout bootstrap script to create a buildout that includes both the setuptools and zc.buildout eggs. This allows you to use the buildout software without modifying a Python install. The buildout script is installed into your buildout local scripts area.
  3. Use a buildoput command from an already installed buildout to bootstrap a new buildout. (See the section on bootstraping later in this document.)

Often, a software project will be managed in a software repository, such as a subversion repository, that includes some software source directories, buildout configuration files, and a copy of the buildout bootstrap script. To work on the project, one would check out the project from the repository and run the bootstrap script which installs setuptools and zc.buildout into the checkout as well as any parts defined.

We have a sample buildout that we created using the bootstrap command of an existing buildout (method 3 above). It has the absolute minimum information. We have bin, develop-eggs, eggs and parts directories, and a configuration file:

>>> ls(sample_buildout)
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
d  parts

The bin directory contains scripts.

>>> ls(sample_buildout, 'bin')
-  buildout
>>> ls(sample_buildout, 'eggs')
-  setuptools-0.6-py2.4.egg
-  zc.buildout-1.0-py2.4.egg

The develop-eggs and parts directories are initially empty:

>>> ls(sample_buildout, 'develop-eggs')
>>> ls(sample_buildout, 'parts')

The develop-eggs directory holds egg links for software being developed in the buildout. We separate develop-eggs and other eggs to allow eggs directories to be shared across multiple buildouts. For example, a common developer technique is to define a common eggs directory in their home that all non-develop eggs are stored in. This allows larger buildouts to be set up much more quickly and saves disk space.

The parts directory provides an area where recipes can install part data. For example, if we built a custom Python, we would install it in the part directory. Part data is stored in a sub-directory of the parts directory with the same name as the part.

Buildouts are defined using configuration files. These are in the format defined by the Python ConfigParser module, with extensions that we’ll describe later. By default, when a buildout is run, it looks for the file buildout.cfg in the directory where the buildout is run.

The minimal configuration file has a buildout section that defines no parts:

>>> cat(sample_buildout, 'buildout.cfg')
[buildout]
parts =

A part is simply something to be created by a buildout. It can be almost anything, such as a Python package, a program, a directory, or even a configuration file.

Recipes

A part is created by a recipe. Recipes are always installed as Python eggs. They can be downloaded from a package server, such as the Python Package Index, or they can be developed as part of a project using a “develop” egg.

A develop egg is a special kind of egg that gets installed as an “egg link” that contains the name of a source directory. Develop eggs don’t have to be packaged for distribution to be used and can be modified in place, which is especially useful while they are being developed.

Let’s create a recipe as part of the sample project. We’ll create a recipe for creating directories. First, we’ll create a recipes source directory for our local recipes:

>>> mkdir(sample_buildout, 'recipes')

and then we’ll create a source file for our mkdir recipe:

>>> write(sample_buildout, 'recipes', 'mkdir.py',
... """
... import logging, os, zc.buildout
...
... class Mkdir:
...
...     def __init__(self, buildout, name, options):
...         self.name, self.options = name, options
...         options['path'] = os.path.join(
...                               buildout['buildout']['directory'],
...                               options['path'],
...                               )
...         if not os.path.isdir(os.path.dirname(options['path'])):
...             logging.getLogger(self.name).error(
...                 'Cannot create %s. %s is not a directory.',
...                 options['path'], os.path.dirname(options['path']))
...             raise zc.buildout.UserError('Invalid Path')
...
...
...     def install(self):
...         path = self.options['path']
...         logging.getLogger(self.name).info(
...             'Creating directory %s', os.path.basename(path))
...         os.mkdir(path)
...         return path
...
...     def update(self):
...         pass
... """)

Currently, recipes must define 3 methods [1]:

  • a constructor,
  • an install method, and
  • an update method.

The constructor is responsible for updating a parts options to reflect data read from other sections. The buildout system keeps track of whether a part specification has changed. A part specification has changed if it’s options, after ajusting for data read from other sections, has changed, or if the recipe has changed. Only the options for the part are considered. If data are read from other sections, then that information has to be reflected in the parts options. In the Mkdir example, the given path is interpreted relative to the buildout directory, and data from the buildout directory is read. The path option is updated to reflect this. If the directory option was changed in the buildout sections, we would know to update parts created using the mkdir recipe using relative path names.

When buildout is run, it saves configuration data for installed parts in a file named “.installed.cfg”. In subsequent runs, it compares part-configuration data stored in the .installed.cfg file and the part-configuration data loaded from the configuration files as modified by recipe constructors to decide if the configuration of a part has changed. If the configuration has changed, or if the recipe has changed, then the part is uninstalled and reinstalled. The buildout only looks at the part’s options, so any data used to configure the part needs to be reflected in the part’s options. It is the job of a recipe constructor to make sure that the options include all relevent data.

Of course, parts are also uninstalled if they are no-longer used.

The recipe defines a constructor that takes a buildout object, a part name, and an options dictionary. It saves them in instance attributes. If the path is relative, we’ll interpret it as relative to the buildout directory. The buildout object passed in is a mapping from section name to a mapping of options for that section. The buildout directory is available as the directory option of the buildout section. We normalize the path and save it back into the options directory.

The install method is responsible for creating the part. In this case, we need the path of the directory to create. We’ll use a path option from our options dictionary. The install method logs what it’s doing using the Python logging call. We return the path that we installed. If the part is uninstalled or reinstalled, then the path returned will be removed by the buildout machinery. A recipe install method is expected to return a string, or an iterable of strings containing paths to be removed if a part is uninstalled. For most recipes, this is all of the uninstall support needed. For more complex uninstallation scenarios use Uninstall recipes.

The update method is responsible for updating an already installed part. An empty method is often provided, as in this example, if parts can’t be updated. An update method can return None, a string, or an iterable of strings. If a string or iterable of strings is returned, then the saved list of paths to be uninstalled is updated with the new information by adding any new files returned by the update method.

We need to provide packaging information so that our recipe can be installed as a develop egg. The minimum information we need to specify [2] is a name. For recipes, we also need to define the names of the recipe classes as entry points. Packaging information is provided via a setup.py script:

>>> write(sample_buildout, 'recipes', 'setup.py',
... """
... from setuptools import setup
...
... setup(
...     name = "recipes",
...     entry_points = {'zc.buildout': ['mkdir = mkdir:Mkdir']},
...     )
... """)

Our setup script defines an entry point. Entry points provide a way for an egg to define the services it provides. Here we’ve said that we define a zc.buildout entry point named mkdir. Recipe classes must be exposed as entry points in the zc.buildout group. we give entry points names within the group.

We also need a README.txt for our recipes to avoid an annoying warning from distutils, on which setuptools and zc.buildout are based:

>>> write(sample_buildout, 'recipes', 'README.txt', " ")

Now let’s update our buildout.cfg:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = mystuff
... """)

Let’s go through the changes one by one:

develop = recipes

This tells the buildout to install a development egg for our recipes. Any number of paths can be listed. The paths can be relative or absolute. If relative, they are treated as relative to the buildout directory. They can be directory or file paths. If a file path is given, it should point to a Python setup script. If a directory path is given, it should point to a directory containing a setup.py file. Development eggs are installed before building any parts, as they may provide locally-defined recipes needed by the parts.

parts = data-dir

Here we’ve named a part to be “built”. We can use any name we want except that different part names must be unique and recipes will often use the part name to decide what to do.

[data-dir]
recipe = recipes:mkdir
path = mystuff

When we name a part, we also create a section of the same name that contains part data. In this section, we’ll define the recipe to be used to install the part. In this case, we also specify the path to be created.

Let’s run the buildout. We do so by running the build script in the buildout:

>>> import os
>>> os.chdir(sample_buildout)
>>> buildout = os.path.join(sample_buildout, 'bin', 'buildout')
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Installing data-dir.
data-dir: Creating directory mystuff

We see that the recipe created the directory, as expected:

>>> ls(sample_buildout)
-  .installed.cfg
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
d  mystuff
d  parts
d  recipes

In addition, .installed.cfg has been created containing information about the part we installed:

>>> cat(sample_buildout, '.installed.cfg')
[buildout]
installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
parts = data-dir
<BLANKLINE>
[data-dir]
__buildout_installed__ = /sample-buildout/mystuff
__buildout_signature__ = recipes-c7vHV6ekIDUPy/7fjAaYjg==
path = /sample-buildout/mystuff
recipe = recipes:mkdir

Note that the directory we installed is included in .installed.cfg. In addition, the path option includes the actual destination directory.

If we change the name of the directory in the configuration file, we’ll see that the directory gets removed and recreated:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = mydata
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling data-dir.
Installing data-dir.
data-dir: Creating directory mydata
>>> ls(sample_buildout)
-  .installed.cfg
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
d  mydata
d  parts
d  recipes

If any of the files or directories created by a recipe are removed, the part will be reinstalled:

>>> rmdir(sample_buildout, 'mydata')
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling data-dir.
Installing data-dir.
data-dir: Creating directory mydata

Error reporting

If a user makes an error, an error needs to be printed and work needs to stop. This is accomplished by logging a detailed error message and then raising a (or an instance of a subclass of a) zc.buildout.UserError exception. Raising an error other than a UserError still displays the error, but labels it as a bug in the buildout software or recipe. In the sample above, of someone gives a non-existant directory to create the directory in:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = /xxx/mydata
... """)

We’ll get a user error, not a traceback.

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
data-dir: Cannot create /xxx/mydata. /xxx is not a directory.
While:
  Installing.
  Getting section data-dir.
  Initializing part data-dir.
Error: Invalid Path

Recipe Error Handling

If an error occurs during installation, it is up to the recipe to clean up any system side effects, such as files created. Let’s update the mkdir recipe to support multiple paths:

>>> write(sample_buildout, 'recipes', 'mkdir.py',
... """
... import logging, os, zc.buildout
...
... class Mkdir:
...
...     def __init__(self, buildout, name, options):
...         self.name, self.options = name, options
...
...         # Normalize paths and check that their parent
...         # directories exist:
...         paths = []
...         for path in options['path'].split():
...             path = os.path.join(buildout['buildout']['directory'], path)
...             if not os.path.isdir(os.path.dirname(path)):
...                 logging.getLogger(self.name).error(
...                     'Cannot create %s. %s is not a directory.',
...                     options['path'], os.path.dirname(options['path']))
...                 raise zc.buildout.UserError('Invalid Path')
...             paths.append(path)
...         options['path'] = ' '.join(paths)
...
...     def install(self):
...         paths = self.options['path'].split()
...         for path in paths:
...             logging.getLogger(self.name).info(
...                 'Creating directory %s', os.path.basename(path))
...             os.mkdir(path)
...         return paths
...
...     def update(self):
...         pass
... """)

If there is an error creating a path, the install method will exit and leave previously created paths in place:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = foo bin
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling data-dir.
Installing data-dir.
data-dir: Creating directory foo
data-dir: Creating directory bin
While:
  Installing data-dir.
<BLANKLINE>
An internal error occured due to a bug in either zc.buildout or in a
recipe being used:
<BLANKLINE>
OSError:
[Errno 17] File exists: '/sample-buildout/bin'

We meant to create a directiry bins, but typed bin. Now foo was left behind.

>>> os.path.exists('foo')
True

If we fix the typo:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = foo bins
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Installing data-dir.
data-dir: Creating directory foo
While:
  Installing data-dir.
<BLANKLINE>
An internal error occured due to a bug in either zc.buildout or in a
recipe being used:
<BLANKLINE>
OSError:
[Errno 17] File exists: '/sample-buildout/foo'

Now they fail because foo exists, because it was left behind.

>>> remove('foo')

Let’s fix the recipe:

>>> write(sample_buildout, 'recipes', 'mkdir.py',
... """
... import logging, os, zc.buildout
...
... class Mkdir:
...
...     def __init__(self, buildout, name, options):
...         self.name, self.options = name, options
...
...         # Normalize paths and check that their parent
...         # directories exist:
...         paths = []
...         for path in options['path'].split():
...             path = os.path.join(buildout['buildout']['directory'], path)
...             if not os.path.isdir(os.path.dirname(path)):
...                 logging.getLogger(self.name).error(
...                     'Cannot create %s. %s is not a directory.',
...                     options['path'], os.path.dirname(options['path']))
...                 raise zc.buildout.UserError('Invalid Path')
...             paths.append(path)
...         options['path'] = ' '.join(paths)
...
...     def install(self):
...         paths = self.options['path'].split()
...         created = []
...         try:
...             for path in paths:
...                 logging.getLogger(self.name).info(
...                     'Creating directory %s', os.path.basename(path))
...                 os.mkdir(path)
...                 created.append(path)
...         except:
...             for d in created:
...                 os.rmdir(d)
...             raise
...
...         return paths
...
...     def update(self):
...         pass
... """)

And put back the typo:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = foo bin
... """)

When we rerun the buildout:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Installing data-dir.
data-dir: Creating directory foo
data-dir: Creating directory bin
While:
  Installing data-dir.
<BLANKLINE>
An internal error occured due to a bug in either zc.buildout or in a
recipe being used:
<BLANKLINE>
OSError:
[Errno 17] File exists: '/sample-buildout/bin'

we get the same error, but we don’t get the directory left behind:

>>> os.path.exists('foo')
False

It’s critical that recipes clean up partial effects when errors occur. Because recipes most commonly create files and directories, buildout provides a helper API for removing created files when an error occurs. Option objects have a created method that can be called to record files as they are created. If the install or update methof returns with an error, then any registered paths are removed automatically. The method returns the files registered and can be used to return the files created. Let’s use this API to simplify the recipe:

>>> write(sample_buildout, 'recipes', 'mkdir.py',
... """
... import logging, os, zc.buildout
...
... class Mkdir:
...
...     def __init__(self, buildout, name, options):
...         self.name, self.options = name, options
...
...         # Normalize paths and check that their parent
...         # directories exist:
...         paths = []
...         for path in options['path'].split():
...             path = os.path.join(buildout['buildout']['directory'], path)
...             if not os.path.isdir(os.path.dirname(path)):
...                 logging.getLogger(self.name).error(
...                     'Cannot create %s. %s is not a directory.',
...                     options['path'], os.path.dirname(options['path']))
...                 raise zc.buildout.UserError('Invalid Path')
...             paths.append(path)
...         options['path'] = ' '.join(paths)
...
...     def install(self):
...         paths = self.options['path'].split()
...         for path in paths:
...             logging.getLogger(self.name).info(
...                 'Creating directory %s', os.path.basename(path))
...             os.mkdir(path)
...             self.options.created(path)
...
...         return self.options.created()
...
...     def update(self):
...         pass
... """)
>>> remove(sample_buildout, 'recipes', 'mkdir.pyc')

We returned by calling created, taking advantage of the fact that it returns the registered paths. We did this for illustrative purposes. It would be simpler just to return the paths as before.

If we rerun the buildout, again, we’ll get the error and no directiories will be created:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Installing data-dir.
data-dir: Creating directory foo
data-dir: Creating directory bin
While:
  Installing data-dir.
<BLANKLINE>
An internal error occured due to a bug in either zc.buildout or in a
recipe being used:
<BLANKLINE>
OSError:
[Errno 17] File exists: '/sample-buildout/bin'
>>> os.path.exists('foo')
False

Now, we’ll fix the typo again and we’ll get the directories we expect:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = foo bins
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Installing data-dir.
data-dir: Creating directory foo
data-dir: Creating directory bins
>>> os.path.exists('foo')
True
>>> os.path.exists('bins')
True

Configuration file syntax

As mentioned earlier, buildout configuration files use the format defined by the Python ConfigParser module with extensions. The extensions are:

  • option names are case sensitive
  • option values can ue a substitution syntax, described below, to refer to option values in specific sections.

The ConfigParser syntax is very flexible. Section names can contain any characters other than newlines and right square braces (“]”). Option names can contain any characters other than newlines, colons, and equal signs, can not start with a space, and don’t include trailing spaces.

It is likely that, in the future, some characters will be given special buildout-defined meanings. This is already true of the characters “:”, “$”, “%”, “(“, and “)”. For now, it is a good idea to keep section and option names simple, sticking to alphanumeric characters, hyphens, and periods.

Variable substitutions

Buildout configuration files support variable substitution. To illustrate this, we’ll create an debug recipe to allow us to see interactions with the buildout:

>>> write(sample_buildout, 'recipes', 'debug.py',
... """
... class Debug:
...
...     def __init__(self, buildout, name, options):
...         self.buildout = buildout
...         self.name = name
...         self.options = options
...
...     def install(self):
...         items = self.options.items()
...         items.sort()
...         for option, value in items:
...             print option, value
...         return ()
...
...     update = install
... """)

This recipe doesn’t actually create anything. The install method doesn’t return anything, because it didn’t create any files or directories.

We also have to update our setup script:

>>> write(sample_buildout, 'recipes', 'setup.py',
... """
... from setuptools import setup
... entry_points = (
... '''
... [zc.buildout]
... mkdir = mkdir:Mkdir
... debug = debug:Debug
... ''')
... setup(name="recipes", entry_points=entry_points)
... """)

We’ve rearranged the script a bit to make the entry points easier to edit. In particular, entry points are now defined as a configuration string, rather than a dictionary.

Let’s update our configuration to provide variable substitution examples:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir debug
... log-level = INFO
...
... [debug]
... recipe = recipes:debug
... File 1 = ${data-dir:path}/file
... File 2 = ${debug:File 1}/log
...
... [data-dir]
... recipe = recipes:mkdir
... path = mydata
... """)

In this example, we’ve used ConfigParser substitutions for file2 and file3. This type of substitution uses Python string format syntax. Valid names are options in the same section and options defined in the DEFAULT section.

We used a string-template substitution for file1. This type of substitution uses the string.Template syntax. Names substituted are qualified option names, consisting of a section name and option name joined by a colon.

Now, if we run the buildout, we’ll see the options with the values substituted.

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling data-dir.
Installing data-dir.
data-dir: Creating directory mydata
Installing debug.
File 1 /sample-buildout/mydata/file
File 2 /sample-buildout/mydata/file/log
recipe recipes:debug

Note that the substitution of the data-dir path option reflects the update to the option performed by the mkdir recipe.

It might seem surprising that mydata was created again. This is because we changed our recipes package by adding the debug module. The buildout system didn’t know if this module could effect the mkdir recipe, so it assumed it could and reinstalled mydata. If we rerun the buildout:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Updating data-dir.
Updating debug.
File 1 /sample-buildout/mydata/file
File 2 /sample-buildout/mydata/file/log
recipe recipes:debug

We can see that mydata was not recreated.

Note that, in this case, we didn’t specify a log level, so we didn’t get output about what the buildout was doing.

Section and option names in variable substitutions are only allowed to contain alphanumeric characters, hyphens, periods and spaces. This restriction might be relaxed in future releases.

Automatic part selection and ordering

When a section with a recipe is refered to, either through variable substitution or by an initializing recipe, the section is treated as a part and added to the part list before the referencing part. For example, we can leave data-dir out of the parts list:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
... log-level = INFO
...
... [debug]
... recipe = recipes:debug
... File 1 = ${data-dir:path}/file
... File 2 = ${debug:File 1}/log
...
... [data-dir]
... recipe = recipes:mkdir
... path = mydata
... """)

It will still be treated as a part:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Updating data-dir.
Updating debug.
File 1 /sample-buildout/mydata/file
File 2 /sample-buildout/mydata/file/log
recipe recipes:debug
>>> cat('.installed.cfg') # doctest: +ELLIPSIS
[buildout]
installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
parts = data-dir debug
...

Note that the data-dir part is included before the debug part, because the debug part refers to the data-dir part. Even if we list the data-dir part after the debug part, it will be included before:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug data-dir
... log-level = INFO
...
... [debug]
... recipe = recipes:debug
... File 1 = ${data-dir:path}/file
... File 2 = ${debug:File 1}/log
...
... [data-dir]
... recipe = recipes:mkdir
... path = mydata
... """)

It will still be treated as a part:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Updating data-dir.
Updating debug.
File 1 /sample-buildout/mydata/file
File 2 /sample-buildout/mydata/file/log
recipe recipes:debug
>>> cat('.installed.cfg') # doctest: +ELLIPSIS
[buildout]
installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
parts = data-dir debug
...

Multiple configuration files

A configuration file can “extend” another configuration file. Options are read from the other configuration file if they aren’t already defined by your configuration file.

The configuration files your file extends can extend other configuration files. The same file may be used more than once although, of course, cycles aren’t allowed.

To see how this works, we use an example:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... extends = base.cfg
...
... [debug]
... op = buildout
... """)
>>> write(sample_buildout, 'base.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
...
... [debug]
... recipe = recipes:debug
... op = base
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Uninstalling data-dir.
Installing debug.
op buildout
recipe recipes:debug

The example is pretty trivial, but the pattern it illustrates is pretty common. In a more practical example, the base buildout might represent a product and the extending buildout might be a customization.

Here is a more elaborate example.

>>> other = tmpdir('other')
>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... extends = b1.cfg b2.cfg %(b3)s
...
... [debug]
... op = buildout
... """ % dict(b3=os.path.join(other, 'b3.cfg')))
>>> write(sample_buildout, 'b1.cfg',
... """
... [buildout]
... extends = base.cfg
...
... [debug]
... op1 = b1 1
... op2 = b1 2
... """)
>>> write(sample_buildout, 'b2.cfg',
... """
... [buildout]
... extends = base.cfg
...
... [debug]
... op2 = b2 2
... op3 = b2 3
... """)
>>> write(other, 'b3.cfg',
... """
... [buildout]
... extends = b3base.cfg
...
... [debug]
... op4 = b3 4
... """)
>>> write(other, 'b3base.cfg',
... """
... [debug]
... op5 = b3base 5
... """)
>>> write(sample_buildout, 'base.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
...
... [debug]
... recipe = recipes:debug
... name = base
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
name base
op buildout
op1 b1 1
op2 b2 2
op3 b2 3
op4 b3 4
op5 b3base 5
recipe recipes:debug

There are several things to note about this example:

  • We can name multiple files in an extends option.
  • We can reference files recursively.
  • Relative file names in extended options are interpreted relative to the directory containing the referencing configuration file.

Loading Configuration from URLs

Configuration files can be loaded from URLs. To see how this works, we’ll set up a web server with some configuration files.

>>> server_data = tmpdir('server_data')
>>> write(server_data, "r1.cfg",
... """
... [debug]
... op1 = r1 1
... op2 = r1 2
... """)
>>> write(server_data, "r2.cfg",
... """
... [buildout]
... extends = r1.cfg
...
... [debug]
... op2 = r2 2
... op3 = r2 3
... """)
>>> server_url = start_server(server_data)
>>> write('client.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
... extends = %(url)s/r2.cfg
...
... [debug]
... recipe = recipes:debug
... name = base
... """ % dict(url=server_url))
>>> print system(buildout+ ' -c client.cfg'),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
name base
op1 r1 1
op2 r2 2
op3 r2 3
recipe recipes:debug

Here we specified a URL for the file we extended. The file we downloaded, itself refered to a file on the server using a relative URL reference. Relative references are interpreted relative to the base URL when they appear in configuration files loaded via URL.

We can also specify a URL as the configuration file to be used by a buildout.

>>> os.remove('client.cfg')
>>> write(server_data, 'remote.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
... extends = r2.cfg
...
... [debug]
... recipe = recipes:debug
... name = remote
... """)
>>> print system(buildout + ' -c ' + server_url + '/remote.cfg'),
While:
  Initializing.
Error: Missing option: buildout:directory

Normally, the buildout directory defaults to directory containing a configuration file. This won’t work for configuration files loaded from URLs. In this case, the buildout directory would normally be defined on the command line:

>>> print system(buildout
...              + ' -c ' + server_url + '/remote.cfg'
...              + ' buildout:directory=' + sample_buildout
...              ),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
name remote
op1 r1 1
op2 r2 2
op3 r2 3
recipe recipes:debug

User defaults

If the file $HOME/.buildout/default.cfg, exists, it is read before reading the configuration file. ($HOME is the value of the HOME environment variable. The ‘/’ is replaced by the operating system file delimiter.)

>>> old_home = os.environ['HOME']
>>> home = tmpdir('home')
>>> mkdir(home, '.buildout')
>>> write(home, '.buildout', 'default.cfg',
... """
... [debug]
... op1 = 1
... op7 = 7
... """)
>>> os.environ['HOME'] = home
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
name base
op buildout
op1 b1 1
op2 b2 2
op3 b2 3
op4 b3 4
op5 b3base 5
op7 7
recipe recipes:debug

A buildout command-line argument, -U, can be used to suppress reading user defaults:

>>> print system(buildout + ' -U'),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
name base
op buildout
op1 b1 1
op2 b2 2
op3 b2 3
op4 b3 4
op5 b3base 5
recipe recipes:debug
>>> os.environ['HOME'] = old_home

Log level

We can control the level of logging by specifying a log level in out configuration file. For example, so suppress info messages, we can set the logging level to WARNING

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... log-level = WARNING
... extends = b1.cfg b2.cfg
... """)
>>> print system(buildout),
name base
op1 b1 1
op2 b2 2
op3 b2 3
recipe recipes:debug

Uninstall recipes

As we’ve seen, when parts are installed, buildout keeps track of files and directories that they create. When the parts are uninstalled these files and directories are deleted.

Sometimes more clean up is needed. For example, a recipe might add a system service by calling chkconfig –add during installation. Later during uninstallation, chkconfig –del will need to be called to remove the system service.

In order to deal with these uninstallation issues, you can register uninstall recipes. Uninstall recipes are registered using the ‘zc.buildout.uninstall’ entry point. Parts specify uninstall recipes using the ‘uninstall’ option.

In comparison to regular recipes, uninstall recipes are much simpler. They are simply callable objects that accept the name of the part to be uninstalled and the part’s options dictionary. Uninstall recipes don’t have access to the part itself since it maybe not be able to be instantiated at uninstallation time.

Here’s a recipe that simulates installation of a system service, along with an uninstall recipe that simulates removing the service.

>>> write(sample_buildout, 'recipes', 'service.py',
... """
... class Service:
...
...     def __init__(self, buildout, name, options):
...         self.buildout = buildout
...         self.name = name
...         self.options = options
...
...     def install(self):
...         print "chkconfig --add %s" % self.options['script']
...         return ()
...
...     def update(self):
...         pass
...
...
... def uninstall_service(name, options):
...     print "chkconfig --del %s" % options['script']
... """)

To use these recipes we must register them using entry points. Make sure to use the same name for the recipe and uninstall recipe. This is required to let buildout know which uninstall recipe goes with which recipe.

>>> write(sample_buildout, 'recipes', 'setup.py',
... """
... from setuptools import setup
... entry_points = (
... '''
... [zc.buildout]
... mkdir = mkdir:Mkdir
... debug = debug:Debug
... service = service:Service
...
... [zc.buildout.uninstall]
... service = service:uninstall_service
... ''')
... setup(name="recipes", entry_points=entry_points)
... """)

Here’s how these recipes could be used in a buildout:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = service
...
... [service]
... recipe = recipes:service
... script = /path/to/script
... """)

When the buildout is run the service will be installed

>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing service.
chkconfig --add /path/to/script
<BLANKLINE>

The service has been installed. If the buildout is run again with no changes, the serivce shouldn’t be changed.

>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Updating service.
<BLANKLINE>

Now we change the service part to trigger uninstallation and re-installation.

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = service
...
... [service]
... recipe = recipes:service
... script = /path/to/a/different/script
... """)
>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Uninstalling service.
Running uninstall recipe.
chkconfig --del /path/to/script
Installing service.
chkconfig --add /path/to/a/different/script
<BLANKLINE>

Now we remove the service part, and add another part.

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
...
... [debug]
... recipe = recipes:debug
... """)
>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Uninstalling service.
Running uninstall recipe.
chkconfig --del /path/to/a/different/script
Installing debug.
recipe recipes:debug
<BLANKLINE>

Uninstall recipes don’t have to take care of removing all the files and directories created by the part. This is still done automatically, following the execution of the uninstall recipe. An upshot is that an uninstallation recipe can access files and directories created by a recipe before they are deleted.

For example, here’s an uninstallation recipe that simulates backing up a directory before it is deleted. It is designed to work with the mkdir recipe introduced earlier.

>>> write(sample_buildout, 'recipes', 'backup.py',
... """
... import os
... def backup_directory(name, options):
...     path = options['path']
...     size = len(os.listdir(path))
...     print "backing up directory %s of size %s" % (path, size)
... """)

It must be registered with the zc.buildout.uninstall entry point. Notice how it is given the name ‘mkdir’ to associate it with the mkdir recipe.

>>> write(sample_buildout, 'recipes', 'setup.py',
... """
... from setuptools import setup
... entry_points = (
... '''
... [zc.buildout]
... mkdir = mkdir:Mkdir
... debug = debug:Debug
... service = service:Service
...
... [zc.buildout.uninstall]
... uninstall_service = service:uninstall_service
... mkdir = backup:backup_directory
... ''')
... setup(name="recipes", entry_points=entry_points)
... """)

Now we can use it with a mkdir part.

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = dir debug
...
... [dir]
... recipe = recipes:mkdir
... path = my_directory
...
... [debug]
... recipe = recipes:debug
... """)

Run the buildout to install the part.

>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing dir.
dir: Creating directory my_directory
Installing debug.
recipe recipes:debug
<BLANKLINE>

Now we remove the part from the configuration file.

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
...
... [debug]
... recipe = recipes:debug
... """)

When the buildout is run the part is removed, and the uninstall recipe is run before the directory is deleted.

>>> print system(buildout)
Develop: '/sample-buildout/recipes'
Uninstalling dir.
Running uninstall recipe.
backing up directory /sample-buildout/my_directory of size 0
Updating debug.
recipe recipes:debug
<BLANKLINE>

Now we will return the registeration to normal for the benefit of the rest of the examples.

>>> write(sample_buildout, 'recipes', 'setup.py',
... """
... from setuptools import setup
... entry_points = (
... '''
... [zc.buildout]
... mkdir = mkdir:Mkdir
... debug = debug:Debug
... ''')
... setup(name="recipes", entry_points=entry_points)
... """)

Command-line usage

A number of arguments can be given on the buildout command line. The command usage is:

buildout [options and assignments] [command [command arguments]]

The following options are supported:

-h (or –help)
Print basic usage information. If this option is used, then all other options are ignored.
-c filename The -c option can be used to specify a configuration file, rather than buildout.cfg in the current directory.
-v Increment the verbosity by 10. The verbosity is used to adjust the logging level. The verbosity is subtracted from the numeric value of the log-level option specified in the configuration file.
-q Decrement the verbosity by 10.
-U Don’t read user-default configuration.
-o Run in off-line mode. This is equivalent to the assignment buildout:offline=true.
-O Run in non-off-line mode. This is equivalent to the assignment buildout:offline=false. This is the default buildout mode. The -O option would normally be used to override a true offline setting in a configuration file.
-n Run in newest mode. This is equivalent to the assignment buildout:newest=true. With this setting, which is the default, buildout will try to find the newest versions of distributions available that satisfy its requirements.
-N Run in non-newest mode. This is equivalent to the assignment buildout:newest=false. With this setting, buildout will not seek new distributions if installed distributions satisfy it’s requirements.

Assignments are of the form:

section_name:option_name=value

Options and assignments can be given in any order.

Here’s an example:

>>> write(sample_buildout, 'other.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
... installed = .other.cfg
... log-level = WARNING
...
... [debug]
... name = other
... recipe = recipes:debug
... """)

Note that we used the installed buildout option to specify an alternate file to store information about installed parts.

>>> print system(buildout+' -c other.cfg debug:op1=foo -v'),
Develop: '/sample-buildout/recipes'
Installing debug.
name other
op1 foo
recipe recipes:debug

Here we used the -c option to specify an alternate configuration file, and the -v option to increase the level of logging from the default, WARNING.

Options can also be combined in the usual Unix way, as in:

>>> print system(buildout+' -vcother.cfg debug:op1=foo'),
Develop: '/sample-buildout/recipes'
Updating debug.
name other
op1 foo
recipe recipes:debug

Here we combined the -v and -c options with the configuration file name. Note that the -c option has to be last, because it takes an argument.

>>> os.remove(os.path.join(sample_buildout, 'other.cfg'))
>>> os.remove(os.path.join(sample_buildout, '.other.cfg'))

The most commonly used command is ‘install’ and it takes a list of parts to install. if any parts are specified, only those parts are installed. To illustrate this, we’ll update our configuration and run the buildout in the usual way:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug d1 d2 d3
...
... [d1]
... recipe = recipes:mkdir
... path = d1
...
... [d2]
... recipe = recipes:mkdir
... path = d2
...
... [d3]
... recipe = recipes:mkdir
... path = d3
...
... [debug]
... recipe = recipes:debug
... """)
>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling debug.
Installing debug.
recipe recipes:debug
Installing d1.
d1: Creating directory d1
Installing d2.
d2: Creating directory d2
Installing d3.
d3: Creating directory d3
>>> ls(sample_buildout)
-  .installed.cfg
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  d1
d  d2
d  d3
d  develop-eggs
d  eggs
d  parts
d  recipes
>>> cat(sample_buildout, '.installed.cfg')
[buildout]
installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
parts = debug d1 d2 d3
<BLANKLINE>
[debug]
__buildout_installed__ =
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
recipe = recipes:debug
<BLANKLINE>
[d1]
__buildout_installed__ = /sample-buildout/d1
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/d1
recipe = recipes:mkdir
<BLANKLINE>
[d2]
__buildout_installed__ = /sample-buildout/d2
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/d2
recipe = recipes:mkdir
<BLANKLINE>
[d3]
__buildout_installed__ = /sample-buildout/d3
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/d3
recipe = recipes:mkdir

Now we’ll update our configuration file:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug d2 d3 d4
...
... [d2]
... recipe = recipes:mkdir
... path = data2
...
... [d3]
... recipe = recipes:mkdir
... path = data3
...
... [d4]
... recipe = recipes:mkdir
... path = ${d2:path}-extra
...
... [debug]
... recipe = recipes:debug
... x = 1
... """)

and run the buildout specifying just d3 and d4:

>>> print system(buildout+' install d3 d4'),
Develop: '/sample-buildout/recipes'
Uninstalling d3.
Installing d3.
d3: Creating directory data3
Installing d4.
d4: Creating directory data2-extra
>>> ls(sample_buildout)
-  .installed.cfg
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  d1
d  d2
d  data2-extra
d  data3
d  develop-eggs
d  eggs
d  parts
d  recipes

Only the d3 and d4 recipes ran. d3 was removed and data3 and data2-extra were created.

The .installed.cfg is only updated for the recipes that ran:

>>> cat(sample_buildout, '.installed.cfg')
[buildout]
installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
parts = debug d1 d2 d3 d4
<BLANKLINE>
[debug]
__buildout_installed__ =
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
recipe = recipes:debug
<BLANKLINE>
[d1]
__buildout_installed__ = /sample-buildout/d1
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/d1
recipe = recipes:mkdir
<BLANKLINE>
[d2]
__buildout_installed__ = /sample-buildout/d2
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/d2
recipe = recipes:mkdir
<BLANKLINE>
[d3]
__buildout_installed__ = /sample-buildout/data3
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/data3
recipe = recipes:mkdir
<BLANKLINE>
[d4]
__buildout_installed__ = /sample-buildout/data2-extra
__buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
path = /sample-buildout/data2-extra
recipe = recipes:mkdir

Note that the installed data for debug, d1, and d2 haven’t changed, because we didn’t install those parts and that the d1 and d2 directories are still there.

Now, if we run the buildout without the install command:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Uninstalling d2.
Uninstalling d1.
Uninstalling debug.
Installing debug.
recipe recipes:debug
x 1
Installing d2.
d2: Creating directory data2
Updating d3.
Updating d4.

We see the output of the debug recipe and that data2 was created. We also see that d1 and d2 have gone away:

>>> ls(sample_buildout)
-  .installed.cfg
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  data2
d  data2-extra
d  data3
d  develop-eggs
d  eggs
d  parts
d  recipes

Alternate directory and file locations

The buildout normally puts the bin, eggs, and parts directories in the directory in the directory containing the configuration file. You can provide alternate locations, and even names for these directories.

>>> alt = tmpdir('sample-alt')
>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts =
... develop-eggs-directory = %(developbasket)s
... eggs-directory = %(basket)s
... bin-directory = %(scripts)s
... parts-directory = %(work)s
... """ % dict(
...    developbasket = os.path.join(alt, 'developbasket'),
...    basket = os.path.join(alt, 'basket'),
...    scripts = os.path.join(alt, 'scripts'),
...    work = os.path.join(alt, 'work'),
... ))
>>> print system(buildout),
Creating directory '/sample-alt/scripts'.
Creating directory '/sample-alt/work'.
Creating directory '/sample-alt/basket'.
Creating directory '/sample-alt/developbasket'.
Develop: '/sample-buildout/recipes'
Uninstalling d4.
Uninstalling d3.
Uninstalling d2.
Uninstalling debug.
>>> ls(alt)
d  basket
d  developbasket
d  scripts
d  work
>>> ls(alt, 'developbasket')
-  recipes.egg-link

You can also specify an alternate buildout directory:

>>> rmdir(alt)
>>> alt = tmpdir('sample-alt')
>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... directory = %(alt)s
... develop = %(recipes)s
... parts =
... """ % dict(
...    alt=alt,
...    recipes=os.path.join(sample_buildout, 'recipes'),
...    ))
>>> print system(buildout),
Creating directory '/sample-alt/bin'.
Creating directory '/sample-alt/parts'.
Creating directory '/sample-alt/eggs'.
Creating directory '/sample-alt/develop-eggs'.
Develop: '/sample-buildout/recipes'
>>> ls(alt)
-  .installed.cfg
d  bin
d  develop-eggs
d  eggs
d  parts
>>> ls(alt, 'develop-eggs')
-  recipes.egg-link

Logging control

Three buildout options are used to control logging:

log-level
specifies the log level
verbosity
adjusts the log level
log-format
allows an alternate logging for mat to be specified

We’ve already seen the log level and verbosity. Let’s look at an example of changing the format:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts =
... log-level = 25
... verbosity = 5
... log-format = %(levelname)s %(message)s
... """)

Here, we’ve changed the format to include the log-level name, rather than the logger name.

We’ve also illustrated, with a contrived example, that the log level can be a numeric value and that the verbosity can be specified in the configuration file. Because the verbosity is subtracted from the log level, we get a final log level of 20, which is the INFO level.

>>> print system(buildout),
INFO Develop: '/sample-buildout/recipes'

Predefined buildout options

Buildouts have a number of predefined options that recipes can use and that users can override in their configuration files. To see these, we’ll run a minimal buildout configuration with a debug logging level. One of the features of debug logging is that the configuration database is shown.

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... parts =
... """)
>>> print system(buildout+' -vv'),
Installing 'zc.buildout', 'setuptools'.
We have a develop egg: zc.buildout 1.0.0.
We have the best distribution that satisfies 'setuptools'.
Picked: setuptools = 0.6
<BLANKLINE>
Configuration data:
[buildout]
bin-directory = /sample-buildout/bin
develop-eggs-directory = /sample-buildout/develop-eggs
directory = /sample-buildout
eggs-directory = /sample-buildout/eggs
executable = /usr/local/bin/python2.3
installed = /sample-buildout/.installed.cfg
log-format =
log-level = INFO
newest = true
offline = false
parts =
parts-directory = /sample-buildout/parts
python = buildout
verbosity = 20
<BLANKLINE>

All of these options can be overridden by configuration files or by command-line assignments. We’ve discussed most of these options already, but let’s review them and touch on some we haven’t discussed:

bin-directory
The directory path where scripts are written. This can be a relative path, which is interpreted relative to the directory option.
develop-eggs-directory
The directory path where development egg links are created for software being created in the local project. This can be a relative path, which is interpreted relative to the directory option.
directory
The buildout directory. This is the base for other buildout file and directory locations, when relative locations are used.
eggs-directory
The directory path where downloaded eggs are put. It is common to share this directory across buildouts. Eggs in this directory should never be modified. This can be a relative path, which is interpreted relative to the directory option.
executable
The Python executable used to run the buildout. See the python option below.
installed
The file path where information about the results of the previous buildout run is written. This can be a relative path, which is interpreted relative to the directory option. This file provides an inventory of installed parts with information needed to decide which if any parts need to be uninstalled.
log-format
The format used for logging messages.
log-level
The log level before verbosity adjustment
parts
A white space separated list of parts to be installed.
parts-directory
A working directory that parts can used to store data.
python
The name of a section containing information about the default Python interpreter. Recipes that need a installation typically have options to tell them which Python installation to use. By convention, if a section-specific option isn’t used, the option is looked for in the buildout section. The option must point to a section with an executable option giving the path to a Python executable. By default, the buildout section defines the default Python as the Python used to run the buildout.
verbosity
A log-level adjustment. Typically, this is set via the -q and -v command-line options.

Creating new buildouts and bootstrapping

If zc.buildout is installed, you can use it to create a new buildout with it’s own local copies of zc.buildout and setuptools and with local buildout scripts.

>>> sample_bootstrapped = tmpdir('sample-bootstrapped')
>>> print system(buildout
...              +' -c'+os.path.join(sample_bootstrapped, 'setup.cfg')
...              +' init'),
Creating '/sample-bootstrapped/setup.cfg'.
Creating directory '/sample-bootstrapped/bin'.
Creating directory '/sample-bootstrapped/parts'.
Creating directory '/sample-bootstrapped/eggs'.
Creating directory '/sample-bootstrapped/develop-eggs'.
Generated script '/sample-bootstrapped/bin/buildout'.

Note that a basic setup.cfg was created for us.

>>> ls(sample_bootstrapped)
d  bin
d  develop-eggs
d  eggs
d  parts
-  setup.cfg
>>> ls(sample_bootstrapped, 'bin')
-  buildout
>>> _ = (ls(sample_bootstrapped, 'eggs'),
...      ls(sample_bootstrapped, 'develop-eggs'))
-  setuptools-0.6-py2.3.egg
-  zc.buildout-1.0-py2.3.egg

(We list both the eggs and develop-eggs diectories because the buildout or setuptools egg could be installed in the develop-eggs directory if the original buildout had develop eggs for either buildout or setuptools.)

Note that the buildout script was installed but not run. To run the buildout, we’d have to run the installed buildout script.

If we have an existing buildout that already has a buildout.cfg, we’ll normally use the bootstrap command instead of init. It will complain if there isn’t a configuration file:

>>> sample_bootstrapped2 = tmpdir('sample-bootstrapped2')
>>> print system(buildout
...              +' -c'+os.path.join(sample_bootstrapped2, 'setup.cfg')
...              +' bootstrap'),
While:
  Initializing.
Error: Couldn't open /sample-bootstrapped2/setup.cfg
>>> write(sample_bootstrapped2, 'setup.cfg',
... """
... [buildout]
... parts =
... """)
>>> print system(buildout
...              +' -c'+os.path.join(sample_bootstrapped2, 'setup.cfg')
...              +' bootstrap'),
Creating directory '/sample-bootstrapped2/bin'.
Creating directory '/sample-bootstrapped2/parts'.
Creating directory '/sample-bootstrapped2/eggs'.
Creating directory '/sample-bootstrapped2/develop-eggs'.
Generated script '/sample-bootstrapped2/bin/buildout'.

Newest and Offline Modes

By default buildout and recipes will try to find the newest versions of distributions needed to satisfy requirements. This can be very time consuming, especially when incrementally working on setting up a buildout or working on a recipe. The buildout newest option can be used to to suppress this. If the newest option is set to false, then new distributions won’t be sought if an installed distribution meets requirements. The newest option can be set to false using the -N command-line option.

The offline option goes a bit further. If the buildout offline option is given a value of “true”, the buildout and recipes that are aware of the option will avoid doing network access. This is handy when running the buildout when not connected to the internet. It also makes buildouts run much faster. This option is typically set using the buildout -o option.

Prefering Final Releases

Currently, when searching for new releases, the newest available release is used. This isn’t usually ideal, as you may get development releaes or alpha releases not ready to be widely used. You can request that final releases be prefered using the prefer final option in the buildout section:

[buildout]
...
prefer-final = true

When the prefer-final option is set to true, then when searching for new releases, final releases are prefered. If there are final releases that satisfy distribution requirements, then those releases are used even if newer non-final releases are available. The buildout prefer-final option can be used to override this behavior.

In buildout version 2, final releases will be prefered by default. You will then need to use a false value for prefer-final to get the newset releases.

Controlling the installation database

The buildout installed uption is used to specify the file used to save information on installed parts. This option is initialized to “.installed.cfg”, but it can be overridded in the configuration file or on the command line:

>>> write('buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = debug
...
... [debug]
... recipe = recipes:debug
... """)
>>> print system(buildout+' buildout:installed=inst.cfg'),
Develop: '/sample-buildout/recipes'
Installing debug.
recipe recipes:debug
>>> ls(sample_buildout)
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
-  inst.cfg
d  parts
d  recipes

The installation database can be disabled by supplying an empty buildout installed opttion:

>>> os.remove('inst.cfg')
>>> print system(buildout+' buildout:installed='),
Develop: '/sample-buildout/recipes'
Installing debug.
recipe recipes:debug
>>> ls(sample_buildout)
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
d  parts
d  recipes

Note that there will be no installation database if there are no parts:

>>> write('buildout.cfg',
... """
... [buildout]
... parts =
... """)
>>> print system(buildout+' buildout:installed=inst.cfg'),
>>> ls(sample_buildout)
-  b1.cfg
-  b2.cfg
-  base.cfg
d  bin
-  buildout.cfg
d  develop-eggs
d  eggs
d  parts
d  recipes

Extensions

An experimental feature allows code to be loaded and run after configuration files have been read but before the buildout has begun any processing. The intent is to allow special plugins such as urllib2 request handlers to be loaded.

To load an extension, we use the extensions option and list one or more distribution requirements, on separate lines. The distributions named will be loaded and any zc.buildout.extensions entry points found will be called with the buildout as an argument.

Let’s create a sample extension in our sample buildout created in the previous section:

>>> mkdir(sample_bootstrapped, 'demo')
>>> write(sample_bootstrapped, 'demo', 'demo.py',
... """
... def ext(buildout):
...     print 'ext', list(buildout)
... """)
>>> write(sample_bootstrapped, 'demo', 'setup.py',
... """
... from setuptools import setup
...
... setup(
...     name = "demo",
...     entry_points = {'zc.buildout.extension': ['ext = demo:ext']},
...     )
... """)

Our extension just prints out the word ‘demo’, and lists the sections found in the buildout passed to it.

We’ll update our buildout.cfg to list the demo directory as a develop egg to be built:

>>> write(sample_bootstrapped, 'buildout.cfg',
... """
... [buildout]
... develop = demo
... parts =
... """)
>>> os.chdir(sample_bootstrapped)
>>> print system(os.path.join(sample_bootstrapped, 'bin', 'buildout')),
Develop: '/sample-bootstrapped/demo'

Now we can add the extensions option. We were a bit tricly and ran the buildout once with the demo develop egg defined but without the extension option. This is because extensions are loaded before the buildout creates develop eggs. We needed to use a separate buildout run to create the develop egg. Normally, when eggs are loaded from the network, we wouldn’t need to do anything special.

>>> write(sample_bootstrapped, 'buildout.cfg',
... """
... [buildout]
... develop = demo
... extensions = demo
... parts =
... """)

We see that our extension is loaded and executed:

>>> print system(os.path.join(sample_bootstrapped, 'bin', 'buildout')),
ext ['buildout']
Develop: '/sample-bootstrapped/demo'
[1]In the future, additional mathods may be added. Older recipes with fewer methods will still be supported.
[2]If we wanted to create a distribution from this package, we would need specify much more information. See the setuptools documentation.

Repeatable buildouts: controlling eggs used

One of the goals of zc.buildout is to provide enough control to make buildouts repeatable. It should be possible to check the buildout configuration files for a project into a version control system and later use the checked in files to get the same buildout, subject to changes in the environment outside the buildout.

An advantage of using Python eggs is that depenencies of eggs used are automatically determined and used. The automatic inclusion of depenent distributions is at odds with the goal of repeatable buildouts.

To support repeatable buildouts, a versions section can be created with options for each distribution name whos version is to be fixed. The section can then be specified via the buildout versions option.

To see how this works, we’ll create two versions of a recipe egg:

>>> mkdir('recipe')
>>> write('recipe', 'recipe.py',
... '''
... class Recipe:
...     def __init__(*a): pass
...     def install(self):
...         print 'recipe v1'
...         return ()
...     update = install
... ''')
>>> write('recipe', 'setup.py',
... '''
... from setuptools import setup
... setup(name='spam', version='1', py_modules=['recipe'],
...       entry_points={'zc.buildout': ['default = recipe:Recipe']},
...       )
... ''')
>>> write('recipe', 'README', '')
>>> print system(buildout+' setup recipe bdist_egg'), # doctest: +ELLIPSIS
Running setup script 'recipe/setup.py'.
...
>>> rmdir('recipe', 'build')
>>> write('recipe', 'recipe.py',
... '''
... class Recipe:
...     def __init__(*a): pass
...     def install(self):
...         print 'recipe v2'
...         return ()
...     update = install
... ''')
>>> write('recipe', 'setup.py',
... '''
... from setuptools import setup
... setup(name='spam', version='2', py_modules=['recipe'],
...       entry_points={'zc.buildout': ['default = recipe:Recipe']},
...       )
... ''')
>>> print system(buildout+' setup recipe bdist_egg'), # doctest: +ELLIPSIS
Running setup script 'recipe/setup.py'.
...

and we’ll configure a buildout to use it:

>>> write('buildout.cfg',
... '''
... [buildout]
... parts = foo
... find-links = %s
...
... [foo]
... recipe = spam
... ''' % join('recipe', 'dist'))

If we run the buildout, it will use version 2:

>>> print system(buildout),
Getting distribution for 'spam'.
Got spam 2.
Installing foo.
recipe v2

We can specify a versions section that lists our recipe and name it in the buildout section:

>>> write('buildout.cfg',
... '''
... [buildout]
... parts = foo
... find-links = %s
... versions = release-1
...
... [release-1]
... spam = 1
... eggs = 2.2
...
... [foo]
... recipe = spam
... ''' % join('recipe', 'dist'))

Here we created a release-1 section listing the version 1 for the spam distribution. We told the buildout to use it by specifying release-1 as in the versions option.

Now, if we run the buildout, we’ll use version 1 of the spam recipe:

>>> print system(buildout),
Getting distribution for 'spam==1'.
Got spam 1.
Uninstalling foo.
Installing foo.
recipe v1

Running the buildout in verbose mode will help us get information about versions used. If we run the buildout in verbose mode without specifying a versions section:

>>> print system(buildout+' buildout:versions= -v'), # doctest: +ELLIPSIS
Installing 'zc.buildout', 'setuptools'.
We have a develop egg: zc.buildout 1.0.0.
We have the best distribution that satisfies 'setuptools'.
Picked: setuptools = 0.6
Installing 'spam'.
We have the best distribution that satisfies 'spam'.
Picked: spam = 2.
Uninstalling foo.
Installing foo.
recipe v2

We’ll get output that includes lines that tell us what versions buildout chose a for us, like:

zc.buildout.easy_install.picked: spam = 2

This allows us to discover versions that are picked dynamically, so that we can fix them in a versions section.

If we run the buildout with the versions section:

>>> print system(buildout+' -v'), # doctest: +ELLIPSIS
Installing 'zc.buildout', 'setuptools'.
We have a develop egg: zc.buildout 1.0.0.
We have the best distribution that satisfies 'setuptools'.
Picked: setuptools = 0.6
Installing 'spam'.
We have the distribution that satisfies 'spam==1'.
Uninstalling foo.
Installing foo.
recipe v1

We won’t get output for the spam distribution, which we didn’t pick, but we will get output for setuptools, which we didn’t specify versions for.

Using a download cache

Normally, when distributions are installed, if any processing is needed, they are downloaded from the internet to a temporary directory and then installed from there. A download cache can be used to avoid the download step. This can be useful to reduce network access and to create source distributions of an entire buildout.

The buildout download-cache option can be used to specify a directory to be used as a download cache.

In this example, we’ll create a directory to hold the cache:

>>> cache = tmpdir('cache')

And set up a buildout that downloads some eggs:

>>> write('buildout.cfg',
... '''
... [buildout]
... parts = eggs
... download-cache = %(cache)s
... find-links = %(link_server)s
...
... [eggs]
... recipe = zc.recipe.egg
... eggs = demo ==0.2
... ''' % globals())

We specified a link server that has some distributions available for download:

>>> print get(link_server),
<html><body>
<a href="demo-0.1-py2.4.egg">demo-0.1-py2.4.egg</a><br>
<a href="demo-0.2-py2.4.egg">demo-0.2-py2.4.egg</a><br>
<a href="demo-0.3-py2.4.egg">demo-0.3-py2.4.egg</a><br>
<a href="demo-0.4c1-py2.4.egg">demo-0.4c1-py2.4.egg</a><br>
<a href="demoneeded-1.0.zip">demoneeded-1.0.zip</a><br>
<a href="demoneeded-1.1.zip">demoneeded-1.1.zip</a><br>
<a href="demoneeded-1.2c1.zip">demoneeded-1.2c1.zip</a><br>
<a href="extdemo-1.4.zip">extdemo-1.4.zip</a><br>
<a href="index/">index/</a><br>
<a href="other-1.0-py2.4.egg">other-1.0-py2.4.egg</a><br>
</body></html>

We’ll enable logging on the link server so we can see what’s going on:

>>> get(link_server+'enable_server_logging')
GET 200 /enable_server_logging
''

We also specified a download cache.

If we run the buildout, we’ll see the eggs installed from the link server as usual:

>>> print system(buildout),
GET 200 /
GET 200 /demo-0.2-py2.4.egg
GET 200 /demoneeded-1.2c1.zip
Installing eggs.
Getting distribution for 'demo==0.2'.
Got demo 0.2.
Getting distribution for 'demoneeded'.
Got demoneeded 1.2c1.
Generated script '/sample-buildout/bin/demo'.

We’ll also get the download cache populated. The buildout doesn’t put files in the cache directly. It creates an intermediate directory, dist:

>>> ls(cache)
d  dist
>>> ls(cache, 'dist')
-  demo-0.2-py2.4.egg
-  demoneeded-1.2c1.zip

If we remove the installed eggs from eggs directory and re-run the buildout:

>>> import os
>>> for  f in os.listdir('eggs'):
...     if f.startswith('demo'):
...         remove('eggs', f)
>>> print system(buildout),
GET 200 /
Updating eggs.
Getting distribution for 'demo==0.2'.
Got demo 0.2.
Getting distribution for 'demoneeded'.
Got demoneeded 1.2c1.

We see that the distributions aren’t downloaded, because they’re downloaded from the cache.

Installing solely from a download cache

A download cache can be used as the basis of application source releases. In an application source release, we want to distribute an application that can be built without making any network accesses. In this case, we distribute a buildout with download cache and tell the buildout to install from the download cache only, without making network accesses. The buildout install-from-cache option can be used to signal that packages should be installed only from the download cache.

Let’s remove our installed eggs and run the buildout with the install-from-cache option set to true:

>>> for  f in os.listdir('eggs'):
...     if f.startswith('demo'):
...         remove('eggs', f)
>>> write('buildout.cfg',
... '''
... [buildout]
... parts = eggs
... download-cache = %(cache)s
... install-from-cache = true
... find-links = %(link_server)s
...
... [eggs]
... recipe = zc.recipe.egg
... eggs = demo
... ''' % globals())
>>> print system(buildout),
Uninstalling eggs.
Installing eggs.
Getting distribution for 'demo'.
Got demo 0.2.
Getting distribution for 'demoneeded'.
Got demoneeded 1.2c1.
Generated script '/sample-buildout/bin/demo'.

Automatic Buildout Updates

When a buildout is run, one of the first steps performed is to check for updates to either zc.buildout or setuptools. To demonstrate this, we’ve creates some “new releases” of buildout and setuptools in a new_releases folder:

>>> ls(new_releases)
d  setuptools
-  setuptools-99.99-py2.4.egg
d  zc.buildout
-  zc.buildout-99.99-py2.4.egg

Let’s update the sample buildout.cfg to look in this area:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... find-links = %(new_releases)s
... index = %(new_releases)s
... parts = show-versions
... develop = showversions
...
... [show-versions]
... recipe = showversions
... """ % dict(new_releases=new_releases))

We’ll also include a recipe that echos the versions of setuptools and zc.buildout used:

>>> mkdir(sample_buildout, 'showversions')
>>> write(sample_buildout, 'showversions', 'showversions.py',
... """
... import pkg_resources
...
... class Recipe:
...
...     def __init__(self, buildout, name, options):
...         pass
...
...     def install(self):
...         for project in 'zc.buildout', 'setuptools':
...             req = pkg_resources.Requirement.parse(project)
...             print project, pkg_resources.working_set.find(req).version
...         return ()
...     update = install
... """)
>>> write(sample_buildout, 'showversions', 'setup.py',
... """
... from setuptools import setup
...
... setup(
...     name = "showversions",
...     entry_points = {'zc.buildout': ['default = showversions:Recipe']},
...     )
... """)

Now if we run the buildout, the buildout will upgrade itself to the new versions found in new releases:

>>> print system(buildout),
Getting distribution for 'zc.buildout'.
Got zc.buildout 99.99.
Getting distribution for 'setuptools'.
Got setuptools 99.99.
Upgraded:
  zc.buildout version 99.99,
  setuptools version 99.99;
restarting.
Generated script '/sample-buildout/bin/buildout'.
Develop: '/sample-buildout/showversions'
Installing show-versions.
zc.buildout 99.99
setuptools 99.99

Our buildout script has been updated to use the new eggs:

>>> cat(sample_buildout, 'bin', 'buildout')
#!/usr/local/bin/python2.4
<BLANKLINE>
import sys
sys.path[0:0] = [
  '/sample-buildout/eggs/zc.buildout-99.99-py2.4.egg',
  '/sample-buildout/eggs/setuptools-99.99-py2.4.egg',
  ]
<BLANKLINE>
import zc.buildout.buildout
<BLANKLINE>
if __name__ == '__main__':
    zc.buildout.buildout.main()

There are a number of cases in which the updates don’t happen. Let’s recreate the sample buildout. One case is the one in which we specify versions of zc.buildout and setuptools for which the don’t match. If we update out configuration file to specify an older version:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... find-links = %(new_releases)s
... index = %(new_releases)s
... parts = show-versions
... develop = showversions
... zc.buildout-version = < 99
... setuptools-version = < 99
...
... [show-versions]
... recipe = showversions
... """ % dict(new_releases=new_releases))

We’ll actually “upgrade” to an earlier version.

>>> print system(buildout),
Upgraded:
  zc.buildout version 1.0.0,
  setuptools version 0.6;
restarting.
Generated script '/sample-buildout/bin/buildout'.
Develop: '/sample-buildout/showversions'
Updating show-versions.
zc.buildout 1.0.0
setuptools 0.6

We won’t upgrade in offline mode:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... find-links = %(new_releases)s
... index = %(new_releases)s
... parts = show-versions
... develop = showversions
...
... [show-versions]
... recipe = showversions
... """ % dict(new_releases=new_releases))
>>> print system(buildout+' -o'),
Develop: '/sample-buildout/showversions'
Updating show-versions.
zc.buildout 1.0.0
setuptools 0.6

Or in non-newest mode:

>>> print system(buildout+' -N'),
Develop: '/sample-buildout/showversions'
Updating show-versions.
zc.buildout 1.0.0
setuptools 0.6

We also won’t upgrade if the buildout script bing run isn’t in the buildouts bin directory. To see this we’ll create a new buildout directory:

>>> sample_buildout2 = tmpdir('sample_buildout2')
>>> write(sample_buildout2, 'buildout.cfg',
... """
... [buildout]
... find-links = %(new_releases)s
... index = %(new_releases)s
... parts =
... """ % dict(new_releases=new_releases))
>>> cd(sample_buildout2)
>>> print system(buildout),
Creating directory '/sample_buildout2/bin'.
Creating directory '/sample_buildout2/parts'.
Creating directory '/sample_buildout2/eggs'.
Creating directory '/sample_buildout2/develop-eggs'.
Getting distribution for 'zc.buildout'.
Got zc.buildout 99.99.
Getting distribution for 'setuptools'.
Got setuptools 99.99.
Not upgrading because not running a local buildout command.
>>> ls('bin')

Debugging buildouts

Buildouts can be pretty complex. When things go wrong, it isn’t always obvious why. Errors can occur due to problems in user input or due to bugs in zc.buildout or recipes. When an error occurs, Python’s post-mortem debugger can be used to inspect the state of the buildout or recipe code were there error occured. To enable this, use the -D option to the buildout. Let’s create a recipe that has a bug:

>>> mkdir(sample_buildout, 'recipes')
>>> write(sample_buildout, 'recipes', 'mkdir.py',
... """
... import os, zc.buildout
...
... class Mkdir:
...
...     def __init__(self, buildout, name, options):
...         self.name, self.options = name, options
...         options['path'] = os.path.join(
...                               buildout['buildout']['directory'],
...                               options['path'],
...                               )
...
...     def install(self):
...         directory = self.options['directory']
...         os.mkdir(directory)
...         return directory
...
...     def update(self):
...         pass
... """)
>>> write(sample_buildout, 'recipes', 'setup.py',
... """
... from setuptools import setup
...
... setup(name = "recipes",
...       entry_points = {'zc.buildout': ['mkdir = mkdir:Mkdir']},
...       )
... """)

And create a buildout that uses it:

>>> write(sample_buildout, 'buildout.cfg',
... """
... [buildout]
... develop = recipes
... parts = data-dir
...
... [data-dir]
... recipe = recipes:mkdir
... path = mystuff
... """)

If we run the buildout, we’ll get an error:

>>> print system(buildout),
Develop: '/sample-buildout/recipes'
Installing data-dir.
While:
  Installing data-dir.
Error: Missing option: data-dir:directory

If we want to debug the error, we can add the -D option. Here’s we’ll supply some input:

>>> print system(buildout+" -D", """\
... up
... p self.options.keys()
... q
... """),
Develop: '/sample-buildout/recipes'
Installing data-dir.
> /zc/buildout/buildout.py(925)__getitem__()
-> raise MissingOption("Missing option: %s:%s" % (self.name, key))
(Pdb) > /sample-buildout/recipes/mkdir.py(14)install()
-> directory = self.options['directory']
(Pdb) ['path', 'recipe']
(Pdb) While:
  Installing data-dir.
Traceback (most recent call last):
  File "/zc/buildout/buildout.py", line 1352, in main
    getattr(buildout, command)(args)
  File "/zc/buildout/buildout.py", line 383, in install
    installed_files = self[part]._call(recipe.install)
  File "/zc/buildout/buildout.py", line 961, in _call
    return f()
  File "/sample-buildout/recipes/mkdir.py", line 14, in install
    directory = self.options['directory']
  File "/zc/buildout/buildout.py", line 925, in __getitem__
    raise MissingOption("Missing option: %s:%s" % (self.name, key))
MissingOption: Missing option: data-dir:directory
<BLANKLINE>
Starting pdb:

Testing Support

The zc.buildout.testing module provides an API that can be used when writing recipe tests. This API is documented below. Many examples of using this API can be found in the zc.buildout, zc.recipe.egg, and zc.recipe.testrunner tests.

zc.buildout.testing.buildoutSetUp(test)

The buildoutSetup function can be used as a doctest setup function. It creates a sample buildout that can be used by tests, changing the current working directory to the sample_buildout. It also adds a number of names to the test namespace:

sample_buildout
This is the name of a buildout with a basic configuration.
buildout
This is the path of the buildout script in the sample buildout.
ls(*path)
List the contents of a directory. The directory path is provided as one or more strings, to be joined with os.path.join.
cat(*path)

Display the contents of a file. The file path is provided as one or more strings, to be joined with os.path.join.

On Windows, if the file doesn’t exist, the function will try adding a ‘-script.py’ suffix. This helps to work around a difference in script generation on windows.

mkdir(*path)
Create a directory. The directory path is provided as one or more strings, to be joined with os.path.join.
rmdir(*path)
Remove a directory. The directory path is provided as one or more strings, to be joined with os.path.join.
remove(*path)
Remove a directory or file. The path is provided as one or more strings, to be joined with os.path.join.
tmpdir(name)

Create a temporary directory with the given name. The directory will be automatically removed at the end of the test. The path of the created directory is returned.

Further, if the the normalize_path normlaizing substitution (see below) is used, then any paths starting with this path will be normalized to:

/name/restofpath

No two temporary directories can be created with the same name. A directory created with tmpdir can be removed with rmdir and recreated.

Note that the sample_buildout directory is created by calling this function.

write(*path_and_contents)
Create a file. The file path is provided as one or more strings, to be joined with os.path.join. The last argument is the file contents.
system(command, input='')
Execute a system command with the given input passed to the command’s standard input. The output (error and regular output) from the command is returned.
get(url)
Get a web page.
cd(*path)

Change to the given directory. The directory path is provided as one or more strings, to be joined with os.path.join.

The directory will be reset at the end of the test.

join(*path)
A convenient reference to os.path.join.
register_teardown(func)
Register a tear-down function. The function will be called with no arguments at the end of the test.
start_server(path)

Start a web server on the given path. The server will be shut down at the end of the test. The server URL is returned.

You can cause the server to start and stop logging it’s output using:

>>> get(server_url+'enable_server_logging')

and:

>>> get(server_url+'enable_server_logging')

This can be useful to see how buildout is interacting with a server.

sdist(setup, dest)
Create a source distribution by running the given setup file and placing the result in the given destination directory. If the setup argument is a directory, the thge setup.py file in that directory is used.
bdist_egg(setup, executable, dest)
Create an egg by running the given setup file with the given Python executable and placing the result in the given destination directory. If the setup argument is a directory, then the setup.py file in that directory is used.
find_python(version)

Find a Python executable for the given version, where version is a string like “2.4”.

This function uses the following strategy to find a Python of the given version:

  • Look for an environment variable of the form PYTHON%(version)s.
  • On windows, look for Pythonm%(version)spython
  • on Unix, try running python%(version)s or just python to get the executable

zc.buildout.testing.buildoutTearDown(test)

Tear down everything set up by zc.buildout.testing.buildoutSetUp. Any functions passed to register_teardown are called as well.

install(project, destination)

Install eggs for a given project into a destination. If the destination is a test object, then the eggs directory of the sample buildout (sample_buildout) defined by the test will be used. Tests will use this to install the distributions for the packages being tested (and their dependencies) into a sample buildout. The egg to be used should already be loaded, by importing one of the modules provided, before calling this function.

install_develop(project, destination)

Like install, but a develop egg is installed even if the current egg if not a develop egg.

Output normalization

Recipe tests often generate output that is dependent on temporary file locations, operating system conventions or Python versions. To deal with these dependencies, we often use zope.testing.renormalizing.RENormalizing to normalize test output. zope.testing.renormalizing.RENormalizing takes pairs of regular expressions and substitutions. The zc.buildout.testing module provides a few helpful variables that define regular-expression/substitution pairs that you can pass to zope.testing.renormalizing.RENormalizing.

normalize_path
Converts tests paths, based on directories created with tmpdir(), to simple paths.
normalize_script
On Unix-like systems, scripts are implemented in single files without suffixes. On windows, scripts are implemented with 2 files, a -script.py file and a .exe file. This normalization converts directory listings of Windows scripts to the form generated on UNix-like systems.
normalize_egg_py
Normalize Python version and platform indicators, if specified, in egg names.

Python API for egg and script installation

The easy_install module provides some functions to provide support for egg and script installation. It provides functionality at the python level that is similar to easy_install, with a few exceptions:

  • By default, we look for new packages and the packages that they depend on. This is somewhat like (and uses) the –upgrade option of easy_install, except that we also upgrade required packages.
  • If the highest-revision package satisfying a specification is already present, then we don’t try to get another one. This saves a lot of search time in the common case that packages are pegged to specific versions.
  • If there is a develop egg that satisfies a requirement, we don’t look for additional distributions. We always give preference to develop eggs.
  • Distutils options for building extensions can be passed.

Distribution installation

The easy_install module provides a function, install, for installing one or more packages and their dependencies. The install function takes 2 positional arguments:

  • An iterable of setuptools requirement strings for the distributions to be installed, and
  • A destination directory to install to and to satisfy requirements from. The destination directory can be None, in which case, no new distributions are downloaded and there will be an error if the needed distributions can’t be found amoung those already installed.

It supports a number of optional keyword arguments:

find-links
A sequence of URLs, file names, or directories to look for links to distributions.
index

The URL of an index server, or almost any other valid URL. :)

If not specified, the Python Package Index, http://cheeseshop.python.org/pypi, is used. You can specify an alternate index with this option. If you use the links option and if the links point to the needed distributions, then the index can be anything and will be largely ignored. In the examples, here, we’ll just point to an empty directory on our link server. This will make our examples run a little bit faster.

executable
A path to a Python executable. Distributions will be installed using this executable and will be for the matching Python version.
path
A list of additional directories to search for locally-installed distributions.
always_unzip
A flag indicating that newly-downloaded distributions should be directories even if they could be installed as zip files.
working_set
An exsiting working set to be augmented with additional distributions, if necessary to satisfy requirements. This allows you to call install multiple times, if necessary, to gather multiple sets of requirements.
newest
A boolian value indicating whether to search for new distributions when already-installed distributions meet the requirement. When this is true, the default, and when the destination directory is not None, then the install function will search for the newest distributions that satisfy the requirements.
versions
A dictionary mapping project names to version numbers to be used when selecting distributions. This can be used to specify a set of distribution versions independent of other requirements.

The install method returns a working set containing the distributions needed to meet the given requirements.

We have a link server that has a number of eggs:

>>> print get(link_server),
<html><body>
<a href="demo-0.1-py2.4.egg">demo-0.1-py2.4.egg</a><br>
<a href="demo-0.2-py2.4.egg">demo-0.2-py2.4.egg</a><br>
<a href="demo-0.3-py2.4.egg">demo-0.3-py2.4.egg</a><br>
<a href="demo-0.4c1-py2.4.egg">demo-0.4c1-py2.4.egg</a><br>
<a href="demoneeded-1.0.zip">demoneeded-1.0.zip</a><br>
<a href="demoneeded-1.1.zip">demoneeded-1.1.zip</a><br>
<a href="demoneeded-1.2c1.zip">demoneeded-1.2c1.zip</a><br>
<a href="extdemo-1.4.zip">extdemo-1.4.zip</a><br>
<a href="index/">index/</a><br>
<a href="other-1.0-py2.4.egg">other-1.0-py2.4.egg</a><br>
</body></html>

Let’s make a directory and install the demo egg to it, using the demo:

>>> dest = tmpdir('sample-install')
>>> import zc.buildout.easy_install
>>> ws = zc.buildout.easy_install.install(
...     ['demo==0.2'], dest,
...     links=[link_server], index=link_server+'index/')

We requested version 0.2 of the demo distribution to be installed into the destination server. We specified that we should search for links on the link server and that we should use the (empty) link server index directory as a package index.

The working set contains the distributions we retrieved.

>>> for dist in ws:
...     print dist
demo 0.2
demoneeded 1.1

We got demoneeded because it was a dependency of demo.

And the actual eggs were added to the eggs directory.

>>> ls(dest)
-  demo-0.2-py2.4.egg
-  demoneeded-1.1-py2.4.egg

If we remove the version restriction on demo, but specify a false value for newest, no new distributions will be installed:

>>> ws = zc.buildout.easy_install.install(
...     ['demo'], dest, links=[link_server], index=link_server+'index/',
...     newest=False)
>>> ls(dest)
-  demo-0.2-py2.4.egg
-  demoneeded-1.1-py2.4.egg

If we leave off the newst option, we’ll get an update for demo:

>>> ws = zc.buildout.easy_install.install(
...     ['demo'], dest, links=[link_server], index=link_server+'index/')
>>> ls(dest)
-  demo-0.2-py2.4.egg
-  demo-0.3-py2.4.egg
-  demoneeded-1.1-py2.4.egg

Note that we didn’t get the newest versions available. There were release candidated for newer versions of both packages. By default, final releases are prefered. We can change this behavior using the prefer_final function:

>>> zc.buildout.easy_install.prefer_final(False)
True

The old setting is returned.

>>> ws = zc.buildout.easy_install.install(
...     ['demo'], dest, links=[link_server], index=link_server+'index/')
>>> for dist in ws:
...     print dist
demo 0.4c1
demoneeded 1.2c1
>>> ls(dest)
-  demo-0.2-py2.4.egg
-  demo-0.3-py2.4.egg
-  demo-0.4c1-py2.4.egg
-  demoneeded-1.1-py2.4.egg
-  demoneeded-1.2c1-py2.4.egg

Let’s put the setting back to the default.

>>> zc.buildout.easy_install.prefer_final(True)
False

We can supply additional distributions. We can also supply specifications for distributions that would normally be found via dependencies. We might do this to specify a sprcific version.

>>> ws = zc.buildout.easy_install.install(
...     ['demo', 'other', 'demoneeded==1.0'], dest,
...     links=[link_server], index=link_server+'index/')
>>> for dist in ws:
...     print dist
demo 0.3
other 1.0
demoneeded 1.0
>>> ls(dest)
-  demo-0.2-py2.4.egg
-  demo-0.3-py2.4.egg
-  demo-0.4c1-py2.4.egg
-  demoneeded-1.0-py2.4.egg
-  demoneeded-1.1-py2.4.egg
-  demoneeded-1.2c1-py2.4.egg
d  other-1.0-py2.4.egg

We can request that eggs be unzipped even if they are zip safe. This can be useful when debugging.

>>> rmdir(dest)
>>> dest = tmpdir('sample-install')
>>> ws = zc.buildout.easy_install.install(
...     ['demo'], dest, links=[link_server], index=link_server+'index/',
...     always_unzip=True)
>>> ls(dest)
d  demo-0.3-py2.4.egg
d  demoneeded-1.1-py2.4.egg
>>> rmdir(dest)
>>> dest = tmpdir('sample-install')
>>> ws = zc.buildout.easy_install.install(
...     ['demo'], dest, links=[link_server], index=link_server+'index/',
...     always_unzip=True)
>>> ls(dest)
d  demo-0.3-py2.4.egg
d  demoneeded-1.1-py2.4.egg

Specifying version information indepenent of requirements

Sometimes it’s useful to specify version information indepenent of normal requirements specifications. For example, a buildout may need to lock down a set of versions, without having to put put version numbers in setup files or part definitions. If a dictionary is passed to the install function, mapping project names to version numbers, then the versions numbers will be used.

>>> ws = zc.buildout.easy_install.install(
...     ['demo'], dest, links=[link_server], index=link_server+'index/',
...     versions = dict(demo='0.2', demoneeded='1.0'))
>>> [d.version for d in ws]
['0.2', '1.0']

In this example, we specified a version for demoneeded, even though we didn’t define a requirement for it. The versions specified apply to depenencies as well as the specified requirements.

If we specify a version that’s incompatible with a requirement, then we’ll get an error:

>>> from zope.testing.loggingsupport import InstalledHandler
>>> handler = InstalledHandler('zc.buildout.easy_install')
>>> import logging
>>> logging.getLogger('zc.buildout.easy_install').propagate = False
>>> ws = zc.buildout.easy_install.install(
...     ['demo >0.2'], dest, links=[link_server],
...     index=link_server+'index/',
...     versions = dict(demo='0.2', demoneeded='1.0'))
Traceback (most recent call last):
...
IncompatibleVersionError: Bad version 0.2
>>> print handler
zc.buildout.easy_install DEBUG
  Installing 'demo >0.2'.
zc.buildout.easy_install ERROR
  The version, 0.2, is not consistent with the requirement, 'demo>0.2'.
>>> handler.clear()

If no versions are specified, a debugging message will be output reporting that a version was picked automatically:

>>> ws = zc.buildout.easy_install.install(
...     ['demo'], dest, links=[link_server], index=link_server+'index/',
...     )
>>> print handler
zc.buildout.easy_install DEBUG
  Installing 'demo'.
zc.buildout.easy_install DEBUG
  We have the best distribution that satisfies 'demo'.
zc.buildout.easy_install DEBUG
  Picked: demo = 0.3
zc.buildout.easy_install DEBUG
  Getting required 'demoneeded'
zc.buildout.easy_install DEBUG
    required by demo 0.3.
zc.buildout.easy_install DEBUG
  We have the best distribution that satisfies 'demoneeded'.
zc.buildout.easy_install DEBUG
  Picked: demoneeded = 1.1
>>> handler.uninstall()
>>> logging.getLogger('zc.buildout.easy_install').propagate = True

The function default_versions can be used to get and set default version information to be used when no version information is passes. If called with an argument, it sets the default versions:

>>> zc.buildout.easy_install.default_versions(dict(demoneeded='1'))
{}

It always returns the previous default versions. If called without an argument, it simply returns the default versions without changing them:

>>> zc.buildout.easy_install.default_versions()
{'demoneeded': '1'}

So with the default versions set, we’ll get the requested version even if the versions option isn’t used:

>>> ws = zc.buildout.easy_install.install(
...     ['demo'], dest, links=[link_server], index=link_server+'index/',
...     )
>>> [d.version for d in ws]
['0.3', '1.0']

Of course, we can unset the default versions by passing an empty dictionary:

>>> zc.buildout.easy_install.default_versions({})
{'demoneeded': '1'}
>>> ws = zc.buildout.easy_install.install(
...     ['demo'], dest, links=[link_server], index=link_server+'index/',
...     )
>>> [d.version for d in ws]
['0.3', '1.1']

Script generation

The easy_install module provides support for creating scripts from eggs. It provides a function similar to setuptools except that it provides facilities for baking a script’s path into the script. This has two advantages:

  • The eggs to be used by a script are not chosen at run time, making startup faster and, more importantly, deterministic.
  • The script doesn’t have to import pkg_resources because the logic that pkg_resources would execute at run time is executed at script-creation time.

The scripts method can be used to generate scripts. Let’s create a destination directory for it to place them in:

>>> import tempfile
>>> bin = tmpdir('bin')

Now, we’ll use the scripts method to generate scripts in this directory from the demo egg:

>>> import sys
>>> scripts = zc.buildout.easy_install.scripts(
...     ['demo'], ws, sys.executable, bin)

the four arguments we passed were:

  1. A sequence of distribution requirements. These are of the same form as setuptools requirements. Here we passed a single requirement, for the version 0.1 demo distribution.
  2. A working set,
  3. The Python executable to use, and
  1. The destination directory.

The bin directory now contains a generated script:

>>> ls(bin)
-  demo

The return value is a list of the scripts generated:

>>> import os, sys
>>> if sys.platform == 'win32':
...     scripts == [os.path.join(bin, 'demo.exe'),
...                 os.path.join(bin, 'demo-script.py')]
... else:
...     scripts == [os.path.join(bin, 'demo')]
True

Note that in Windows, 2 files are generated for each script. A script file, ending in ‘-script.py’, and an exe file that allows the script to be invoked directly without having to specify the Python interpreter and without having to provide a ‘.py’ suffix.

The demo script run the entry point defined in the demo egg:

>>> cat(bin, 'demo') # doctest: +NORMALIZE_WHITESPACE
#!/usr/local/bin/python2.4
<BLANKLINE>
import sys
sys.path[0:0] = [
  '/sample-install/demo-0.3-py2.4.egg',
  '/sample-install/demoneeded-1.1-py2.4.egg',
  ]
<BLANKLINE>
import eggrecipedemo
<BLANKLINE>
if __name__ == '__main__':
    eggrecipedemo.main()

Some things to note:

  • The demo and demoneeded eggs are added to the beginning of sys.path.
  • The module for the script entry point is imported and the entry point, in this case, ‘main’, is run.

Rather than requirement strings, you can pass tuples containing 3 strings:

  • A script name,
  • A module,
  • An attribute expression for an entry point within the module.

For example, we could have passed antry point information directly rather than passing a requirement:

>>> scripts = zc.buildout.easy_install.scripts(
...     [('demo', 'eggrecipedemo', 'main')],
...     ws, sys.executable, bin)
>>> cat(bin, 'demo') # doctest: +NORMALIZE_WHITESPACE
#!/usr/local/bin/python2.4
<BLANKLINE>
import sys
sys.path[0:0] = [
  '/sample-install/demo-0.3-py2.4.egg',
  '/sample-install/demoneeded-1.1-py2.4.egg',
  ]
<BLANKLINE>
import eggrecipedemo
<BLANKLINE>
if __name__ == '__main__':
    eggrecipedemo.main()

Passing entry-point information directly is handy when using eggs (or distributions) that don’t declare their entry points, such as distributions that aren’t based on setuptools.

The interpreter keyword argument can be used to generate a script that can be used to invoke the Python interactive interpreter with the path set based on the working set. This generated script can also be used to run other scripts with the path set on the working set:

>>> scripts = zc.buildout.easy_install.scripts(
...     ['demo'], ws, sys.executable, bin, interpreter='py')
>>> ls(bin)
-  demo
-  py
>>> if sys.platform == 'win32':
...     scripts == [os.path.join(bin, 'demo.exe'),
...                 os.path.join(bin, 'demo-script.py'),
...                 os.path.join(bin, 'py.exe'),
...                 os.path.join(bin, 'py-script.py')]
... else:
...     scripts == [os.path.join(bin, 'demo'),
...                 os.path.join(bin, 'py')]
True

The py script simply runs the Python interactive interpreter with the path set:

>>> cat(bin, 'py') # doctest: +NORMALIZE_WHITESPACE
#!/usr/local/bin/python2.4
import sys
<BLANKLINE>
sys.path[0:0] = [
  '/sample-install/demo-0.3-py2.4.egg',
  '/sample-install/demoneeded-1.1-py2.4.egg',
  ]
<BLANKLINE>
_interactive = True
if len(sys.argv) > 1:
    import getopt
    _options, _args = getopt.getopt(sys.argv[1:], 'ic:')
    _interactive = False
    for (_opt, _val) in _options:
        if _opt == '-i':
            _interactive = True
        elif _opt == '-c':
            exec _val
<BLANKLINE>
    if _args:
        sys.argv[:] = _args
        execfile(sys.argv[0])
<BLANKLINE>
if _interactive:
    import code
    code.interact(banner="", local=globals())

If invoked with a script name and arguments, it will run that script, instead.

An additional argumnet can be passed to define which scripts to install and to provide script names. The argument is a dictionary mapping original script names to new script names.

>>> bin = tmpdir('bin2')
>>> scripts = zc.buildout.easy_install.scripts(
...    ['demo'], ws, sys.executable, bin, dict(demo='run'))
>>> if sys.platform == 'win32':
...     scripts == [os.path.join(bin, 'run.exe'),
...                 os.path.join(bin, 'run-script.py')]
... else:
...     scripts == [os.path.join(bin, 'run')]
True
>>> ls(bin)
-  run
>>> print system(os.path.join(bin, 'run')),
3 1

Including extra paths in scripts

We can pass a keyword argument, extra paths, to caue additional paths to be included in the a generated script:

>>> scripts = zc.buildout.easy_install.scripts(
...    ['demo'], ws, sys.executable, bin, dict(demo='run'),
...    extra_paths=['/foo/bar'])
>>> cat(bin, 'run') # doctest: +NORMALIZE_WHITESPACE
#!/usr/local/bin/python2.4
<BLANKLINE>
import sys
sys.path[0:0] = [
  '/sample-install/demo-0.3-py2.4.egg',
  '/sample-install/demoneeded-1.1-py2.4.egg',
  '/foo/bar',
  ]
<BLANKLINE>
import eggrecipedemo
<BLANKLINE>
if __name__ == '__main__':
    eggrecipedemo.main()

Providing script arguments

An “argument” keyword argument can be used to pass arguments to an entry point. The value passed is a source string to be placed between the parentheses in the call:

>>> scripts = zc.buildout.easy_install.scripts(
...    ['demo'], ws, sys.executable, bin, dict(demo='run'),
...    arguments='1, 2')
>>> cat(bin, 'run') # doctest: +NORMALIZE_WHITESPACE
#!/usr/local/bin/python2.4
import sys
sys.path[0:0] = [
  '/sample-install/demo-0.3-py2.4.egg',
  '/sample-install/demoneeded-1.1-py2.4.egg',
  ]
<BLANKLINE>
import eggrecipedemo
<BLANKLINE>
if __name__ == '__main__':
    eggrecipedemo.main(1, 2)

Passing initialization code

You can also pass script initialization code:

>>> scripts = zc.buildout.easy_install.scripts(
...    ['demo'], ws, sys.executable, bin, dict(demo='run'),
...    arguments='1, 2',
...    initialization='import os\nos.chdir("foo")')
>>> cat(bin, 'run') # doctest: +NORMALIZE_WHITESPACE
#!/usr/local/bin/python2.4
import sys
sys.path[0:0] = [
  '/sample-install/demo-0.3-py2.4.egg',
  '/sample-install/demoneeded-1.1-py2.4.egg',
  ]
<BLANKLINE>
import os
os.chdir("foo")
<BLANKLINE>
import eggrecipedemo
<BLANKLINE>
if __name__ == '__main__':
    eggrecipedemo.main(1, 2)

Handling custom build options for extensions provided in source distributions

Sometimes, we need to control how extension modules are built. The build function provides this level of control. It takes a single package specification, downloads a source distribution, and builds it with specified custom build options.

The build function takes 3 positional arguments:

spec
A package specification for a source distribution
dest
A destination directory
build_ext
A dictionary of options to be passed to the distutils build_ext command when building extensions.

It supports a number of optional keyword arguments:

links
a sequence of URLs, file names, or directories to look for links to distributions,
index

The URL of an index server, or almost any other valid URL. :)

If not specified, the Python Package Index, http://cheeseshop.python.org/pypi, is used. You can specify an alternate index with this option. If you use the links option and if the links point to the needed distributions, then the index can be anything and will be largely ignored. In the examples, here, we’ll just point to an empty directory on our link server. This will make our examples run a little bit faster.

executable
A path to a Python executable. Distributions will ne installed using this executable and will be for the matching Python version.
path
A list of additional directories to search for locally-installed distributions.
newest
A boolian value indicating whether to search for new distributions when already-installed distributions meet the requirement. When this is true, the default, and when the destination directory is not None, then the install function will search for the newest distributions that satisfy the requirements.
versions
A dictionary mapping project names to version numbers to be used when selecting distributions. This can be used to specify a set of distribution versions independent of other requirements.

Our link server included a source distribution that includes a simple extension, extdemo.c:

#include <Python.h>
#include <extdemo.h>

static PyMethodDef methods[] = {};

PyMODINIT_FUNC
initextdemo(void)
{
    PyObject *m;
    m = Py_InitModule3("extdemo", methods, "");
#ifdef TWO
    PyModule_AddObject(m, "val", PyInt_FromLong(2));
#else
    PyModule_AddObject(m, "val", PyInt_FromLong(EXTDEMO));
#endif
}

The extension depends on a system-dependent include file, extdemo.h, that defines a constant, EXTDEMO, that is exposed by the extension.

We’ll add an include directory to our sample buildout and add the needed include file to it:

>>> mkdir('include')
>>> write('include', 'extdemo.h',
... """
... #define EXTDEMO 42
... """)

Now, we can use the build function to create an egg from the source distribution:

>>> zc.buildout.easy_install.build(
...   'extdemo', dest,
...   {'include-dirs': os.path.join(sample_buildout, 'include')},
...   links=[link_server], index=link_server+'index/')
['/sample-install/extdemo-1.4-py2.4-unix-i686.egg']

The function returns the list of eggs

Now if we look in our destination directory, we see we have an extdemo egg:

>>> ls(dest)
-  demo-0.2-py2.4.egg
d  demo-0.3-py2.4.egg
-  demoneeded-1.0-py2.4.egg
d  demoneeded-1.1-py2.4.egg
d  extdemo-1.4-py2.4-unix-i686.egg

Let’s update our link server with a new version of extdemo:

>>> update_extdemo()
>>> print get(link_server),
<html><body>
<a href="demo-0.1-py2.4.egg">demo-0.1-py2.4.egg</a><br>
<a href="demo-0.2-py2.4.egg">demo-0.2-py2.4.egg</a><br>
<a href="demo-0.3-py2.4.egg">demo-0.3-py2.4.egg</a><br>
<a href="demo-0.4c1-py2.4.egg">demo-0.4c1-py2.4.egg</a><br>
<a href="demoneeded-1.0.zip">demoneeded-1.0.zip</a><br>
<a href="demoneeded-1.1.zip">demoneeded-1.1.zip</a><br>
<a href="demoneeded-1.2c1.zip">demoneeded-1.2c1.zip</a><br>
<a href="extdemo-1.4.zip">extdemo-1.4.zip</a><br>
<a href="extdemo-1.5.zip">extdemo-1.5.zip</a><br>
<a href="index/">index/</a><br>
<a href="other-1.0-py2.4.egg">other-1.0-py2.4.egg</a><br>
</body></html>

The easy_install caches information about servers to reduce network access. To see the update, we have to call the clear_index_cache function to clear the index cache:

>>> zc.buildout.easy_install.clear_index_cache()

If we run build with newest set to False, we won’t get an update:

>>> zc.buildout.easy_install.build(
...   'extdemo', dest,
...   {'include-dirs': os.path.join(sample_buildout, 'include')},
...   links=[link_server], index=link_server+'index/',
...   newest=False)
['/sample-install/extdemo-1.4-py2.4-linux-i686.egg']
>>> ls(dest)
-  demo-0.2-py2.4.egg
d  demo-0.3-py2.4.egg
-  demoneeded-1.0-py2.4.egg
d  demoneeded-1.1-py2.4.egg
d  extdemo-1.4-py2.4-unix-i686.egg

But if we run it with the default True setting for newest, then we’ll get an updated egg:

>>> zc.buildout.easy_install.build(
...   'extdemo', dest,
...   {'include-dirs': os.path.join(sample_buildout, 'include')},
...   links=[link_server], index=link_server+'index/')
['/sample-install/extdemo-1.5-py2.4-unix-i686.egg']
>>> ls(dest)
-  demo-0.2-py2.4.egg
d  demo-0.3-py2.4.egg
-  demoneeded-1.0-py2.4.egg
d  demoneeded-1.1-py2.4.egg
d  extdemo-1.4-py2.4-unix-i686.egg
d  extdemo-1.5-py2.4-unix-i686.egg

The versions option also influences the versions used. For example, if we specify a version for extdemo, then that will be used, even though it isn’t the newest. Let’s clean out the destimation directory first:

>>> import os
>>> for name in os.listdir(dest):
...     remove(dest, name)
>>> zc.buildout.easy_install.build(
...   'extdemo', dest,
...   {'include-dirs': os.path.join(sample_buildout, 'include')},
...   links=[link_server], index=link_server+'index/',
...   versions=dict(extdemo='1.4'))
['/sample-install/extdemo-1.4-py2.4-unix-i686.egg']
>>> ls(dest)
d  extdemo-1.4-py2.4-unix-i686.egg

Handling custom build options for extensions in develop eggs

The develop function is similar to the build function, except that, rather than building an egg from a source directory containing a setup.py script.

The develop function takes 2 positional arguments:

setup
The path to a setup script, typically named “setup.py”, or a directory containing a setup.py script.
dest
The directory to install the egg link to

It supports some optional keyword argument:

build_ext
A dictionary of options to be passed to the distutils build_ext command when building extensions.
executable
A path to a Python executable. Distributions will ne installed using this executable and will be for the matching Python version.

We have a local directory containing the extdemo source:

>>> ls(extdemo)
-  MANIFEST
-  MANIFEST.in
-  README
-  extdemo.c
-  setup.py

Now, we can use the develop function to create a develop egg from the source distribution:

>>> zc.buildout.easy_install.develop(
...   extdemo, dest,
...   {'include-dirs': os.path.join(sample_buildout, 'include')})
'/sample-install/extdemo.egg-link'

The name of the egg link created is returned.

Now if we look in our destination directory, we see we have an extdemo egg link:

>>> ls(dest)
d  extdemo-1.4-py2.4-unix-i686.egg
-  extdemo.egg-link

And that the source directory contains the compiled extension:

>>> ls(extdemo)
-  MANIFEST
-  MANIFEST.in
-  README
d  build
-  extdemo.c
d  extdemo.egg-info
-  extdemo.so
-  setup.py

Download cache

Normally, when distributions are installed, if any processing is needed, they are downloaded from the internet to a temporary directory and then installed from there. A download cache can be used to avoid the download step. This can be useful to reduce network access and to create source distributions of an entire buildout.

A download cache is specified by calling the download_cache function. The function always returns the previous setting. If no argument is passed, then the setting is unchanged. If an argument is passed, the download cache is set to the given path, which must point to an existing directory. Passing None clears the cache setting.

To see this work, we’ll create a directory and set it as the cache directory:

>>> cache = tmpdir('cache')
>>> zc.buildout.easy_install.download_cache(cache)

We’ll recreate our destination directory:

>>> remove(dest)
>>> dest = tmpdir('sample-install')

We’d like to see what is being fetched from the server, so we’ll enable server logging:

>>> get(link_server+'enable_server_logging')
GET 200 /enable_server_logging
''

Now, if we install demo, and extdemo:

>>> ws = zc.buildout.easy_install.install(
...     ['demo==0.2'], dest,
...     links=[link_server], index=link_server+'index/',
...     always_unzip=True)
GET 200 /
GET 404 /index/demo/
GET 200 /index/
GET 200 /demo-0.2-py2.4.egg
GET 404 /index/demoneeded/
GET 200 /demoneeded-1.1.zip
GET 404 /index/setuptools/
>>> zc.buildout.easy_install.build(
...   'extdemo', dest,
...   {'include-dirs': os.path.join(sample_buildout, 'include')},
...   links=[link_server], index=link_server+'index/')
GET 404 /index/extdemo/
GET 200 /extdemo-1.5.zip
['/sample-install/extdemo-1.5-py2.4-linux-i686.egg']

Not only will we get eggs in our destination directory:

>>> ls(dest)
d  demo-0.2-py2.4.egg
d  demoneeded-1.1-py2.4.egg
d  extdemo-1.5-py2.4-linux-i686.egg

But we’ll get distributions in the cache directory:

>>> ls(cache)
-  demo-0.2-py2.4.egg
-  demoneeded-1.1.zip
-  extdemo-1.5.zip

The cache directory contains uninstalled distributions, such as zipped eggs or source distributions.

Let’s recreate our destination directory and clear the index cache:

>>> remove(dest)
>>> dest = tmpdir('sample-install')
>>> zc.buildout.easy_install.clear_index_cache()

Now when we install the distributions:

>>> ws = zc.buildout.easy_install.install(
...     ['demo==0.2'], dest,
...     links=[link_server], index=link_server+'index/',
...     always_unzip=True)
GET 200 /
GET 404 /index/demo/
GET 200 /index/
GET 404 /index/demoneeded/
GET 404 /index/setuptools/
>>> zc.buildout.easy_install.build(
...   'extdemo', dest,
...   {'include-dirs': os.path.join(sample_buildout, 'include')},
...   links=[link_server], index=link_server+'index/')
GET 404 /index/extdemo/
['/sample-install/extdemo-1.5-py2.4-linux-i686.egg']
>>> ls(dest)
d  demo-0.2-py2.4.egg
d  demoneeded-1.1-py2.4.egg
d  extdemo-1.5-py2.4-linux-i686.egg

Note that we didn’t download the distributions from the link server.

If we remove the restriction on demo, we’ll download a newer version from the link server:

>>> ws = zc.buildout.easy_install.install(
...     ['demo'], dest,
...     links=[link_server], index=link_server+'index/',
...     always_unzip=True)
GET 200 /demo-0.3-py2.4.egg

Normally, the download cache is the prefered source of downloads, but not the only one.

Installing solely from a download cache

A download cache can be used as the basis of application source releases. In an application source release, we want to distribute an application that can be built without making any network accesses. In this case, we distribute a download cache and tell the easy_install module to install from the download cache only, without making network accesses. The install_from_cache function can be used to signal that packages should be installed only from the download cache. The function always returns the previous setting. Calling it with no arguments returns the current setting without changing it:

>>> zc.buildout.easy_install.install_from_cache()
False

Calling it with a boolean value changes the setting and returns the previous setting:

>>> zc.buildout.easy_install.install_from_cache(True)
False

Let’s remove demo-0.3-py2.4.egg from the cache, clear the index cache, recreate the destination directory, and reinstall demo:

>>> for  f in os.listdir(cache):
...     if f.startswith('demo-0.3-'):
...         remove(cache, f)
>>> zc.buildout.easy_install.clear_index_cache()
>>> remove(dest)
>>> dest = tmpdir('sample-install')
>>> ws = zc.buildout.easy_install.install(
...     ['demo'], dest,
...     links=[link_server], index=link_server+'index/',
...     always_unzip=True)
>>> ls(dest)
d  demo-0.2-py2.4.egg
d  demoneeded-1.1-py2.4.egg

This time, we didn’t download from or even query the link server.

 
File Type Py Version Uploaded on Size
zc.buildout-1.0.0b30-py2.3.egg (md5) Python Egg 2.3 2007-08-20 712KB
zc.buildout-1.0.0b30-py2.4.egg (md5) Python Egg 2.4 2007-08-20 172KB
zc.buildout-1.0.0b30-py2.5.egg (md5) Python Egg 2.5 2007-08-20 171KB