Question

I am trying to implement string unescaping with Python regex and backreferences, and it doesn’t seem to want to work very well. I’m sure it’s something I’m doing wrong but I can’t figure out what…

>>> import re >>> mystring = r'This is \n a test \r' >>> p = re.compile( '\\\\(\\S)' ) >>> p.sub( '\\1', mystring ) 'This is n a test r' >>> p.sub( '\\\\\\1', mystring ) 'This is \\n a test \\r' >>> p.sub( '\\\\1', mystring ) 'This is \\1 a test \\1' 

I’d like to replace \\[char] with \[char], but backreferences in Python don’t appear to follow the same rules they do in every other implementation I’ve ever used. Could someone shed some light?

Answer 1

Isn’t that what Anders’ second example does?

In 2.5 there’s also a string-escape encoding you can apply:

>>> mystring = r'This is \n a test \r' >>> mystring.decode('string-escape') 'This is \n a test \r' >>> print mystring.decode('string-escape') This is   a test  >>>