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PODifferences in re.findall and re.finditer -- bug in Python 2.7 re module?
 

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    <p>While demonstrating Python's regex functionality, I wrote a small program to compare the return values of <code>re.search()</code>, <code>re.findall()</code> and <code>re.finditer()</code>. I'm aware that <code>re.search()</code> will only find one match per line and that <code>re.findall()</code> only returns the matched substring(s) and not any location information. However, I was surprised see to see that the matched substring can differ between the three functions.</p> <p>Code (<a href="https://gist.github.com/palday/7805267" rel="nofollow">available on GitHub</a>):</p> <pre><code>#! /usr/bin/env python # -*- coding: utf-8 -*- # License: CC-BY-NC-SA 3.0 import re import codecs # download kate_chopin_the_awakening_and_other_short_stories.txt # from Project Gutenberg: # http://www.gutenberg.org/ebooks/160.txt.utf-8 # with wget: # wget http://www.gutenberg.org/ebooks/160.txt.utf-8 -O kate_chopin_the_awakening_and_other_short_stories.txt # match for something o'clock, with valid numerical time or # any English word with proper capitalization oclock = re.compile(r""" ( [A-Z]?[a-z]+ # word mit max. 1 capital letter | 1[012] # 10,11,12 | [1-9] # 1,2,3,5,6,7,8,9 ) \s o'clock""", re.VERBOSE) path = "kate_chopin_the_awakening_and_other_short_stories.txt" print print "re.search()" print print u"{:&gt;6} {:&gt;6} {:&gt;6}\t{}".format("Line","Start","End","Match") print u"{:=&gt;6} {:=&gt;6} {:=&gt;6}\t{}".format('','','','=====') with codecs.open(path,mode='r',encoding='utf-8') as f: for lineno, line in enumerate(f): atime = oclock.search(line) if atime: print u"{:&gt;6} {:&gt;6} {:&gt;6}\t{}".format(lineno, atime.start(), atime.end(), atime.group()) print print "re.findall()" print print u"{:&gt;6} {:&gt;6} {:&gt;6}\t{}".format("Line","Start","End","Match") print u"{:=&gt;6} {:=&gt;6} {:=&gt;6}\t{}".format('','','','=====') with codecs.open(path,mode='r',encoding='utf-8') as f: for lineno, line in enumerate(f): times = oclock.findall(line) if times: print u"{:&gt;6} {:&gt;6} {:&gt;6}\t{}".format(lineno, '', '', ' '.join(times)) print print "re.finditer()" print print u"{:&gt;6} {:&gt;6} {:&gt;6}\t{}".format("Line","Start","End","Match") print u"{:=&gt;6} {:=&gt;6} {:=&gt;6}\t{}".format('','','','=====') with codecs.open(path,mode='r',encoding='utf-8') as f: for lineno, line in enumerate(f): times = oclock.finditer(line) for m in times: print u"{:&gt;6} {:&gt;6} {:&gt;6}\t{}".format(lineno, m.start(), m.end(), m.group()) </code></pre> <p>and Output (tested on Python 2.7.3 and 2.7.5):</p> <pre><code>re.search() Line Start End Match ====== ====== ====== ===== 248 7 21 eleven o'clock 1520 24 35 one o'clock 1975 21 33 nine o'clock 2106 4 16 four o'clock 4443 19 30 ten o'clock re.findall() Line Start End Match ====== ====== ====== ===== 248 eleven 1520 one 1975 nine 2106 four 4443 ten re.finditer() Line Start End Match ====== ====== ====== ===== 248 7 21 eleven o'clock 1520 24 35 one o'clock 1975 21 33 nine o'clock 2106 4 16 four o'clock 4443 19 30 ten o'clock </code></pre> <p>What am I missing something here? Why doesn't <code>re.findall()</code> return the <code>o'clock</code> bit?</p>
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