Fill paragraph (Python recipe) by Chris Arndt

ActiveState Code (http://code.activestate.com/recipes/134571/)

#!/usr/bin/env python
"""Contains a function to do word-wrapping on text paragraphs."""

__version__ = '0.1'
__author__ = "Christopher Arndt <chris.arndt@web.de"

import re, random

def justify_line(line, width):
    """Stretch a line to width by filling in spaces at word gaps.

    The gaps are picked randomly one-after-another, before it starts
    over again.

    """
    i = []
    while 1:
        # line not long enough already?
        if len(' '.join(line)) < width:
            if not i:
                # index list is exhausted
                # get list if indices excluding last word
                i = range(max(1, len(line)-1))
                # and shuffle it
                random.shuffle(i)
            # append space to a random word and remove its index
            line[i.pop(0)] += ' '
        else:
            # line has reached specified width or wider
            return ' '.join(line)


def fill_paragraphs(text, width=80, justify=0):
    """Split a text into paragraphs and wrap them to width linelength.

    Optionally justify the paragraphs (i.e. stretch lines to fill width).

    Inter-word space is reduced to one space character and paragraphs are
    always separated by two newlines. Indention is currently also lost.

    """
    # split taxt into paragraphs at occurences of two or more newlines
    paragraphs = re.split(r'\n\n+', text)
    for i in range(len(paragraphs)):
        # split paragraphs into a list of words
        words = paragraphs[i].strip().split()
        line = []; new_par = []
        while 1:
           if words:
               if len(' '.join(line + [words[0]])) > width and line:
                   # the line is already long enough -> add it to paragraph
                   if justify:
                       # stretch line to fill width
                       new_par.append(justify_line(line, width))
                   else:
                       new_par.append(' '.join(line))
                   line = []
               else:
                   # append next word
                   line.append(words.pop(0))
           else:
               # last line in paragraph
               new_par.append(' '.join(line))
               line = []
               break
        # replace paragraph with formatted version
        paragraphs[i] = '\n'.join(new_par)
    # return paragraphs separated by two newlines
    return '\n\n'.join(paragraphs)


def _test(width=78, justify=1):
    """Module test case."""
        
    s ="""
This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. 
This is some text. This is some text. This is some text. 

This is some text. This is some text. This is some text. 
This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. This is some text. 
This is some text. This is some text. 
This is some text.

This is some text. 
This is some text. 
This is some text. This is some text. 
This is some text. This is some text. This is some text. 
"""
    print fill_paragraphs(s, width, justify)

if __name__ == '__main__':
    _test()