CODEWITHSUNDEEP
pythonregexpython-2.7
Raj
Raj

Reputation: 2398

Referring capture group in re.match() in python

Hi this is the string I want to match

mystr = "mykey/20161010/20161010"

so far my regex is like this

re.match("mykey/([2-9][0-9][0-9][0-9][0-1][0-9][0-3][0-9])/[.]*", mystr)

As you can see, I am using One Capture group. I want to replace the [.]* by referring the Capture group I have already created. How should I do this?

PS : I am using Python 2.7

Update 1 Based on the answers so far, I have tried this(I have simplified the example little bit), but does not seem to be working...

>>> mystr = "mykey/20/20"

>>> print re.match("mykey\/([2-9][0-9])\/[.]*", mystr)
<_sre.SRE_Match object at 0x7faf96ddf558>

>>> print re.match("mykey\/([2-9][0-9])\/.*", mystr)
<_sre.SRE_Match object at 0x7faf96ddf558>

>>> print re.match("mykey\/([2-9][0-9])\/\1", mystr)
None

I am getting None when trying to refer the Capture group. Am I missing something?

Update 2: Finally Working... Hope this helps someone looking for the answer. Adding additional backslash(ie \) did the trick

>>> import re
>>> mystr = "mykey/20160610/20160610"
>>> re.match("mykey/([2-9][0-9][0-9][0-9][0-1][0-9][0-3][0-9])/\\1", mystr)
<_sre.SRE_Match object at 0x7fe352145558>

Upvotes: 0

Views: 217

Answers (1)

Vamsi Prabhala
Vamsi Prabhala

Reputation: 49260

mykey\/([2-9][0-9][0-9][0-9][0-1][0-9][0-3][0-9])\/\1

Use \1 - to capture the exact match produced by the first capturing group which is [2-9][0-9][0-9][0-9][0-1][0-9][0-3][0-9] in this case.

Shorter version of the same would be 

mykey\/([2-9]\d{3}[0-1]\d[0-3]\d)\/\1

Upvotes: 2

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