Regular expressions

Load some text from a file

Imagine you have some text, say from a text file:

text = open("pg105.txt").read()

Finding a pattern in a loop

for match in re.findall(r"the \w+", text):
    print match

   the use
   the terms
   the Project
   the Baronetage
   the limited
   the earliest
   the almost
   the last
   the page
   the favourite

for match in re.findall(r"the (\w+)", text):
    print match

   use
   terms
   Project
   Baronetage
   limited
   earliest
   almost
   last
   page
   favourite

for match in re.findall(r"(\w+) the (\w+)", text):
    print match

   ('for', 'use')
   ('under', 'terms')
   ('of', 'Project')
   ('but', 'Baronetage')
   ('contemplating', 'limited')
   ('of', 'earliest')
   ('over', 'almost')
   ('of', 'last')
   ('was', 'page')
   ('which', 'favourite')

Search & Replace with .sub

print re.sub(r"the (\w+)", r"the ONLY \1", text)

   The Project Gutenberg EBook of Persuasion, by Jane Austen

   This eBook is for the ONLY use of anyone anywhere at no cost and with
   almost no restrictions whatsoever.  You may copy it, give it away or
   re-use it under the ONLY terms of the ONLY Project Gutenberg License included
   with this eBook or online at www.gutenberg.net