Why regular expression pattern does not match only in Python?

Question

I tested the pattern on notepad++ and python regular expression test web sites and it works great. But in python it does not match. regex.search method returns None.

Text:

├¢  Downloads      : 20314 times                                      
├¢  Language       : English                                       
├¢  Format         : srt                                           
├¢  Total          : 1 subtitle file

Pattern:

^.{1,3}\s+(.*?):\s+(.*?)$

Script:

 with open('file.txt','r',encoding='utf-8') as f:
        string = f.read()
        print(string)
        pattern = r'^.{1,3}\s+(.*?):\s+(.*?)$'
        regex = re.compile(pattern)
        match = regex.search(string,re.UNICODE|re.M)
        print( 'Matching "%s"' % pattern)
        print ('  ', match.group())
        print ('  ', match.groupdict())

I consider myself pretty good at regex, but I'm having a hard time wrapping my head around the purpose of `(.*?)` — user590028, Jul 28 '15 at 18:34
@user590028, the added `?` makes the search expression lazy. For an explanation, see http://stackoverflow.com/questions/2301285/what-do-lazy-and-greedy-mean-in-the-context-of-regular-expressions — aaaantoine, Jul 28 '15 at 18:53
@user590028 The first group in pattern is a key, and the second group in pattern is a value. I am trying to figure key/value pairs out in regex. — RockOnGom, Jul 28 '15 at 18:56

score 2 · Accepted Answer · answered Jul 28 '15 at 18:45

You need to apply the flags in re.compile() function not in search :

>>> regex = re.compile(pattern,re.U|re.M)
>>> regex.search(st)
<_sre.SRE_Match object at 0x7f367951b2d8>
>>> regex.search(st).group()
u'\u251c\xa2  Downloads      : 20314 times

If you apply the flags in re.search it will returns None :

>>> regex = re.compile(pattern)
>>> regex.search(st,re.U|re.M).group()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'group'

Why regular expression pattern does not match only in Python?

1 Answers1