don 0.1.1

Requirements

This module should be used with Python 3.4 or any later version of Python interpreter.

This module depends only on the Python standard library. It does not depend on any third party libraries.

Installation

You can install this package using pip3 using the following command.

pip3 install don

You can install this package from source distribution. To do so, download the latest .tar.gz file from https://pypi.python.org/pypi/don, extract it, then open command prompt or shell, and change your current directory to the directory where you extracted the source distribution, and then execute the following command.

python3 setup.py install

Note that on a Windows system, you may have to replace python3 with the path to your Python 3 interpreter.

Support

To report any bugs, or ask any question, please visit https://github.com/susam/don/issues.

Resources

Here is a list of useful links about this project.

• Latest release on PyPI

• Source code on GitHub

• Issue tracker on GitHub

• Changelog on GitHub

License

This is free software. You are permitted to redistribute and use it in source and binary forms, with or without modification, under the terms of the Simplified BSD License. See the LICENSE.rst file for the complete license.

This software is provided WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the LICENSE.rst file for the complete disclaimer.

Getting started

Here is a very simple example of DON.

title: Countries

india.capital: New Delhi
india.demonym: Indian
india.driving: Left

italy.capital: Rome
italy.demonym: Italian
italy.driving: Right

The above DON specifies three top-level DON attributes (also known as root attributes). They are title, india and italy. The title attribute is a string attribute. The value of title is Countries. However, india and italy are object attributes. The value of india is an object which contains three attributes: capital, demonym and driving.

The root object is an object of type don.Object. This is a dictionary that supports accessing its keys as attributes as well. Therefore, for the above example, title, india and italy are keys in the root object. The value of string attributes are of type str. The value of object attributes are of type don.Object.

The following Python code demonstrates how the don module may be used to parse the above example DON into a root DON object, and then access the attributes.

import don

# An example DON
s = """
title: Countries

india.capital: New Delhi
india.demonym: Indian
india.driving: Left

italy.capital: Rome
italy.demonym: Italian
italy.driving: Right
"""

# Parse DON
root = don.parse(s)

# Access a root attribute
print(root.title)

# Access object attributes in various ways
print(root.india.capital)       # As attributes
print(root['india']['demonym']) # As dictionary keys
print(root.india['driving'])    # In a mixed fashion

# An object attribute is actually a dictionary
print(root.italy)

Here is the output of the above program.

Countries
New Delhi
Indian
Left
{'driving': 'Right', 'capital': 'Rome', 'demonym': 'Italian'}

This is all there is to parsing a DON string into an object and accessing its attributes.

DON syntax

A DON string or DON file contains a list of key value pairs. Each key value pair is separated by a colon. Here is an example.

fruit: mango
drink: beer
level: debug

Empty lines, lines consisting of whitespace characters only and lines beginning with the hash character, i.e. #, are ignored. Therefore, lines beginning with # may be used to write comments. The following DON example is equivalent to the previous example.

# Eat and drink
fruit: mango
drink: beer

# Logging level
level: debug

Further, any leading whitespace before a key or a value, and any trailing whitespace after a key or value are ignored. The following DON example is equivalent to the previous example.

# Eat and drink
  fruit : mango
    drink: beer

  # Logging level
level:debug

A DON string represents a single object, known as the root object, that contains attributes. For example, when the above example is parsed by DON parser, the string is converted into a root object (which we will call as root). This root object in turn contains three attributes with three values. In this case, all three values happen to be strings, so these attributes may be called string attributes.

The keys in DON may be one or more dot separated tokens. Each token must be a valid Python identifier. Here is an example that shows dot separated tokens as keys.

process.priority: normal
process.protocol: tcp
process.log.file: log.txt
process.log.level: debug
process.log.rotate: daily

In this example, the root object contains an object attribute called process which in turn contains two string attributes called priority and protocol, and one object attribute called log. The log attribute in turn contains three string attributes called file, level and rotate.

Here is a tree diagram that shows the relationship between the various attributes.

(root)
 `-- process
     |-- priority
     |-- protocol
     `-- log
         |-- file
         |-- level
         `-- rotate

This is a DON tree. The root node is known as the root object. The internal nodes are always object attributes. They contain one or more other attributes as their values. The leaf nodes are always string attributes. They contain strings as their values.

A key may contain one or more empty tokens before any non-empty token. An empty token in a key is equivalent to the corresponding token in its previous key, i.e. the Nth empty token in a key is a synonym for the Nth token in its previous key. An empty token must appear before any non-empty token. The number of empty tokens in a key must not exceed the number of tokens in its previous key. According to these rules, the following DON example is equivalent to the previous example.

process.priority: normal
.protocol: tcp
.log.file: log.txt
..level: debug
..rotate: daily

Since leading and trailing whitespace characters around keys and values are ignored, the keys with empty tokens may be indented to improve readability.

process.priority: normal
       .protocol: tcp
       .log.file: log.txt
          ..level: debug
          ..rotate: daily

When a key is followed by empty value, it only declares the key. It does not define anything. It does not cause the DON tree to be updated. Declaring a key is useful for using empty tokens in the following keys, so that the empty tokens in the following keys become synonyms of the corresponding tokens in the declared key. This can improve readability quite significantly as shown by the following DON example which is equivalent to the previous example.

process:
    .priority: normal
    .protocol: tcp
    .log:
        ..file: log.txt
        ..level: debug
        ..rotate: daily