Simple python regex doubt

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November 20th, 2012, 01:55 PM

prodigyaj

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Simple python regex doubt

Hi,

I am trying to get a match for the string "test?" Below compilation doesnt yield a match

regex = re.compile(r'\w\?')
print regex.match('test?')

Any leads on why? Sorry if this a very basic question as this my first attempt on python regex.

Thanks
- AJ

November 20th, 2012, 02:11 PM

b49P23TIvg

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>>> import re
>>> re.search('test[?]',"this is a test?")
<_sre.SRE_Match object at 0x15e81d0>
>>> re.search('test[?]',"this is a test")
>>>

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November 20th, 2012, 02:14 PM

prodigyaj

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Thanks for the reply. Can you please explain in a couple of sentences why my code is not right and how is this piece of code u gave works?

Thanks again !
- AJ

November 20th, 2012, 02:50 PM

SuperOscar

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Quote:

Originally Posted by prodigyaj

Can you please explain in a couple of sentences why my code is not right and how is this piece of code u gave works?

Let the docs speak: “Note that even in MULTILINE mode, re.match() will only match at the beginning of the string and not at the beginning of each line.”

http://docs.python.org/3/library/re.html

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November 20th, 2012, 04:48 PM

b49P23TIvg

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Your
r'\w'
matches only a single character, making SuperOscar's explanation dead on correct.

>>> re.match(r'\w+\?','thisisatest?')
<_sre.SRE_Match object at 0x1a1ff38>

The + permits 1 or more of prior expression.

Code:

>>> o = re.search(r'\w+\?','this is a test?')
>>> o.string[slice(*o.span())]
'test?'
>>>

Comments on this post

prodigyaj agrees!

Last edited by b49P23TIvg : November 20th, 2012 at 05:02 PM. Reason: demonstrate that that works

November 21st, 2012, 05:17 AM

SuperOscar

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I have to admit I didn’t even read very thoroughly the regex in question. When first I stumbled into this strange feature of Python’s .match() method – one I still quite can’t understand – I decided always to use .search() since it makes much more sense.

Comments on this post

b49P23TIvg agrees: re.match doesn't belong.

November 21st, 2012, 11:09 AM

prodigyaj

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Thanks ! It helped me understand

Simple python regex doubt

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