Python: Regex to split paragraphs into sentences.

""" To be adapted for extracting features for document classification.
    Original from Stack Overflow;
 http://stackoverflow.com/questions/8465335/a-regex-for-extracting-sentence-from-a-paragraph-in-python
"""

import re as re

def splitParagraphIntoSentences(paragraph):
    sentenceEnders = re.compile(r"""
        # Split sentences on whitespace between them.
        (?:               # Group for two positive lookbehinds.
          (?<=[.!?])      # Either an end of sentence punct,
        | (?<=[.!?]['"])  # or end of sentence punct and quote.
        )                 # End group of two positive lookbehinds.
        (?<!  Mr\.   )    # Don't end sentence on "Mr."
        (?<!  Mrs\.  )
        (?<!  Ms\.   )
        (?<!  Jr\.   )
        (?<!  Dr\.   )
        (?<!  Prof\. )
        (?<!  Sr\.   )
        \s+               # Split on whitespace between sentences.
        """,
        re.IGNORECASE | re.VERBOSE)
    return sentenceEnders.split(paragraph)

if __name__ == '__main__':
    f = open("your_fav.txt", 'r')
    text = f.read()
    sentences = splitParagraphIntoSentences(text)
    longsentences = 0
    sentencecount = 0
    totalwords = 0
    for i in sentences:
        print i.strip()       # Voila, a sentence
        lst1 = i.split(' ')
        print "sentence length",len(lst1)
        if len(lst1) > 20: longsentences += 1
        sentencecount += 1
        totalwords += len(lst1)
        print '------------------------------------------------------'
    print "Number of sentences =",sentencecount
    print "Number of words     =",totalwords
    print "Long sentences      =",longsentences
    print "Av sentence length  =",(totalwords+0.0)/sentencecount