Re:What is \1 here?

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From	Dave Angel <davea@davea.name>
Subject	Re:What is \1 here?
Date	Tue, 11 Nov 2014 07:22:44 -0500 (EST)
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satishmlmlml@gmail.com Wrote in message:
> What does \1 do in the following piece of code(fourth line)?
> import re
> print(re.sub('[ABC]', '*', 'XAXAXBXBXCXC'))
> print(re.sub('[ABC]_', '*', 'XA-XA_XB-XB_XC-XC_'))
> print(re.sub('(.) spam', 'spam\\1', 'x spam, y spam'))
> def mapper(matchobj):
>        return 'spam' + matchobj.group(1)
> print(re.sub('(.) spam', mapper, 'x spam, y spam'))
> 
> 

Recommend you use raw strings when defining regex patterns.  Then
 you wouldn't have to double the backslash.

To see what re.sub will see, try
print ('spam\\1')

As for what the function does with that, I'll have to guess, as I
 don't do regex. I'd guess it'll match any digit.

-- 
DaveA

Thread

What is \1 here? satishmlmlml@gmail.com - 2014-11-11 01:18 -0800
  Re: What is \1 here? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-11-11 10:03 +0000
  Re: What is \1 here? Ned Batchelder <ned@nedbatchelder.com> - 2014-11-11 06:52 -0500
  Re:What is \1 here? Dave Angel <davea@davea.name> - 2014-11-11 07:22 -0500
  Re: What is \1 here? Denis McMahon <denismfmcmahon@gmail.com> - 2014-11-11 17:35 +0000

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