SaltyCrane Blog — Notes on JavaScript and web development

Python finditer regular expression example

I often process text line by line using the splitlines() method with a for loop. This works great most of the time, however, sometimes, the text is not neatly divisible into lines, or, I need to match multiple items per line. This is where the re module's finditer function can help. finditer returns an iterator over all non-overlapping matches for the regular expression pattern in the string. (See docs.) It is a powerful tool for text processing and one that I don't use often enough.

Here is a simple example which demonstrates the use of finditer. It reads in a page of html text, finds all the occurrences of the word "the" and prints "the" and the following word. It also prints the character position of each match using the MatchObject's start() method. (See docs.) Note that, for simplicity, I didn't mess with the HTML tags at all. I just pretended it was plain text. Oh, and the example text is taken from Steve Yegge's article: How To Make a Funny Talk Title Without Using The Word "Weasel"

Python code:

import re
import urllib2

html = urllib2.urlopen('').read()
pattern = r'\b(the\s+\w+)\s+'
regex = re.compile(pattern, re.IGNORECASE)
for match in regex.finditer(html):
    print "%s: %s" % (match.start(),


1301: The Word
12291: The Word
13367: the cut
14025: the car
15050: the free
15513: the third
15558: the sessions
15617: the ONLY
15684: the ground
15911: the OSI
15933: The Attack
16051: The gist
16115: the term
16178: the creator
16741: the thing
16850: the same
16877: the thing
16942: the next
17131: the talk
17374: the room
17727: the hell
17782: the term
17830: the 1980s
18083: the whole
18158: the same
18230: the mountain
18305: the seat
18537: The pro
18718: the banner
18928: the poor
19006: the midst
19223: the buzzwagon
19326: the source
19437: the OSI
19855: the OSI
19927: the other
20055: the Ten
20404: The 22
20517: the OSI
20616: the book
21098: the collective
21553: the proposed
21681: the Five
21932: the nearest
22690: The rest
22858: the entertaining
23255: the crap
23561: the next
23661: the registration
23963: the registration
24114: the restaurant
24289: the people
24456: the second
24597: the current
24871: The Style
24929: the front
25047: the curtain
25132: the movie
25159: The hospital
25249: the night
25881: the way
25892: the rear
25927: the crowd
26194: the podium
26262: the front
26521: the door
26593: the front
26622: The economist
27128: the thing
27228: The next
27290: the Pirate
27409: the material
27461: the crowd
27621: the next
27916: The technician
28084: the way
28487: the technician
28735: the exciting
35709: The Next
36587: The Pinocchio
45436: the Kingdom
45679: The Truth
51623: the same
52526: The Word


#1 Clem120% commented on :

Yes regex are best for this kind of thing, you can optimize your code :



re.compile(pattern, re.IGNORECASE)

regex = re.compile(pattern)

print "%s: %s" % (match.start(),

print match.start(),

#2 Farooq Khan commented on :

it =regex.finditer(html)
for match in it: