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say 0.311

Simple formatted printing with templates. E.g.: say("Hello, {whoever}!")

Latest Version: 1.2.1

This module is supplementd or replaced Python's print statement/function, format function/method, and % string interpolation operator with higher-level facilities.

Q: It's been forty years since C introduced printf() and the basic formatted printing of positional parameters. Isn't it time for an upgrade?

A: Yes! ZOMG, yes!

say provides straightforward string formatting with a DRY, Pythonic templating approach. It piggybacks the format() method, using its formatting syntax (and underlying engine).

Usage

from say import say, fmt

x = 12
nums = list(range(4))

say("There are {x} things.")
say("Nums has {len(nums)} items: {nums}")

yields:

There are 12 things.
Nums has 4 items: [1, 2, 3, 4]

say is basically a simpler, nicer recasting of:

print "There are {} things.".format(x)
print "Nums has {} items: {}".format(len(nums), nums)

The more items that are being printed, and the complicated the format invocation, the more valuable having it stated in-line becomes. Note that full expressions are are supported. They are evaluated in the context of the caller.

Printing Where You Like

say() writes to a list of files--by default just sys.stdout. But with it simple configuration call, it will write to different--even multiple-- files:

from say import say, stdout

say.setfiles(stdout, "report.txt")
say(...)   # now prints to both stdout and report.txt

This has the advantage of allowing you to capture program output without changing any code. You can also define your own targeted Say instances:

from say import say, Say, stderr

err = say.clone().setfiles([stderr, 'error.txt'])
err("Failed with error {errcode}")  # writes to stderr, error.txt

Printing When You Like

If you want to stop printing for a while:

say.set(silent=True)  # no printing until set to False

Or transiently:

say(...stuff..., silent=not verbose) # prints iff bool(verbose) is True

Of course, you don't have to print to any file. There's a predefined sayer fmt() that works exactly like say() and inherits most of its options, but doesn't print. (The C analogy: say : fmt :: printf : sprintf.)

Encodings

say() and fmt() try to work with Unicode strings, for example providing them as return values. But character encodings remain a fractious and often exasperating part of IT. When writing to files, say handles this with an

If you are using Python 2.7 with strings containing utf-8 rather than Unicode characters, say will not be greatly happy--but basically in the same places that format() is already not happy.

When writing to files under Python 2.7, say writes using an encoding (by default, utf-8). But you can get creative:

say('I am a truck!', encoding='base64')  # SSBhbSBhIHRydWNrIQo=

Or change the default:

say.set(encoding='rot-13')

Knock yourself out with all the exciting opportunites! If you really want the formatted text returned just as it is written to files, use the encoded option. Set to True it returns text in the output encoding. Or set to anything else, that becomes the return encoding.

say() returns the formatted text with one small tweak: it removes the final newline if a newline is the very last character. Though odd, this is exactly what you need if you're going to print or say the resulting text without a gratuitous "extra" newline.

Titles and Horizontal Rules

say defines a few convenience formatting functions:

say.title('Errors', sep='-')
for i,e in enumerate(errors, start=1):
    say("{i:3}: {e['name'].upper()}")

might yield:

--------------- Errors ---------------
  1: I/O ERROR
  2: COMPUTE ERROR

A similar method hr produces just a horizontal line, like the HTML <hr> element. For either, one can optionally specify the width (width), character repeated to make the line (sep), and vertical separation/whitespace above and below the item (vsep). Good options for the separator might be be '-', '=', or parts of the Unicode box drawing character set.

Python 3

Say works the same way in both Python 2 and Python 3. This can simplify software that should work across the versions, without all the from __future__ import hassle.

say attempts to mask some of the quirky compexities of the 2-to-3 divide, such as string encodings and codec use.

Alternatives

  • ScopeFormatter is a module that provides variable interpolation into strings. It is amazingly compact and elegant. Sadly, it only interpolates Python names, not full expressions. say has full expressions, as well as a framework for higher-level printing features beyond ScopeFormatter's...um...scope.

  • Even simpler are invocations of % or format() using locals(). E.g.:

    name = "Joe"
    print "Hello, %(name)!" % locals()
    # or
    print "Hello, {name}!".format(**locals())
    

    Unfortunately this has even more limitations than ScopeFormatter: it only supports local variables, not globals or expressions. And the interpolation code seems gratuitous. Simpler:

    say("Hello, {name}!")
    

Notes

  • The say name was inspired by Perl's say, but the similarity stops there.
  • Automated multi-version testing with the wonderful pytest and tox modules has commenced. say is now successfully packaged for, and tested against, all late-model verions of Python: 2.6, 2.7, 3.2, and 3.3.
  • say has greater ambitions than just simple template printing. It's part of a larger rethinking of how output should be formatted. Stay tuned.
  • In addition to being a practical module in its own right, say is testbed for options, a package that provides high-flexibility option, configuration, and parameter management.
  • The author, Jonathan Eunice or @jeunice on Twitter welcomes your comments and suggestions.

Installation

pip install say

To easy_install under a specific Python version (3.3 in this example):

python3.3 -m easy_install say

(You may need to prefix these with "sudo " to authorize installation.)

 
File Type Py Version Uploaded on Size
say-0.311.tar.gz (md5) Source 2012-10-18 9KB
say-0.311.zip (md5) Source 2012-10-18 17KB
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