Bernard Lebel wrote: > Hello, > > I have a string, and I use a regular expression to search a match in > it. When I find one, I would like to break down the string, using the > matched part of it, to be able to perform some formatting and to later > build a brand new string with the separate parts. > > The regular expression part works ok, but my problem is to extract the > matched pattern from the string. I'm not sure how to do that... > > > sString = 'mt_03_04_04_anim' > > # Create regular expression object > oRe = re.compile( "\d\d_\d\d\_\d\d" ) > > # Break-up path > aString = sString.split( os.sep ) > > # Iterate individual components > for i in range( 0, len( aString ) ): > > sSubString = aString[i] > > # Search with shot number of 2 digits > oMatch = oRe.search( sSubString ) > > if oMatch != None: > # Replace last sequence of two digits by 3 digits!!
Hi Bernard, It sounds like you need to put some groups into your regex and use re.sub(). By putting groups in the regex you can refer to pieces of the match. For example >>> import re >>> s = 'mt_03_04_04_anim' >>> oRe = re.compile( "(\d\d_\d\d\_)(\d\d)" ) >>> m = oRe.search(s) >>> m.group(1) '03_04_' >>> m.group(2) '04' With re.sub(), you provide a replacement pattern that can refer to the groups from the match pattern. So to insert new characters between the groups is easy: >>> oRe.sub(r'\1XX\2', s) 'mt_03_04_XX04_anim' This may be enough power to do what you want, I'm not sure from your description. But re.sub() has another trick up its sleeve - the replacement 'expression' can be a callable which is passed the match object and returns the string to replace it with. For example, if you wanted to find all the two digit numbers in a string and add one to them, you could do it like this: >>> def incMatch(m): ... s = m.group(0) # use the whole match ... return str(int(s)+1).zfill(2) ... >>> re.sub(r'\d\d', incMatch, '01_09_23') '02_10_24' This capability can be used to do complicated replacements. Kent _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
