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I'm parsing a file and looking in the lines for username-# where the username will change and there can be any number of digits [0-9] after the dash.

I have tried nearly every combination trying to use the variable username in the regular expression.

Am I even close with something like re.compile('%s-\d*'%user)?

user
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utahwithak
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4 Answers4

22

Working as it should:

>>> user = 'heinz'
>>> import re
>>> regex = re.compile('%s-\d*'%user)
>>> regex.match('heinz-1')
<_sre.SRE_Match object at 0x2b27a18e3f38>
>>> regex.match('heinz-11')
<_sre.SRE_Match object at 0x2b27a2f7c030>
>>> regex.match('heinz-12345')
<_sre.SRE_Match object at 0x2b27a18e3f38>
>>> regex.match('foo-12345')
  • I feel really stupid now. So why is it that when I try and create it in a pdb break it gives me a syntaxerror – utahwithak May 05 '11 at 16:00
  • In the python debugger, it wouldn't let me create it as I was stepping through. Isn't the debugger a normal python interpreter? http://docs.python.org/library/pdb.html – utahwithak May 05 '11 at 16:06
  • WHat are you talking about? The code is copy-pasted from the interactive console? Are you trying to copy-pasted code in your debugger? –  May 05 '11 at 16:07
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    Make sure to use `re.escape()` as @Steven said in his answer. E.g. `regex = re.compile('%s-\d*'%re.escape(user))`. – jtpereyda Sep 17 '15 at 23:48
3

You could create the string using .format() method of string:

re.compile('{}-\d*'.format(user))
John Gaines Jr.
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3

Yes, concatenate the regex yourself, or use string formatting. But don't forget to use re.escape() if your variable could contain characters that have special meaning in regular expressions.

Steven
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0

What about:

re.compile(user + '-\d*')
hsz
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