On 23 oct, 13:54, Peter Otten <__pete...@web.de> wrote: > abdulet wrote: > > Well its this normal? i want to concatenate a number to a > > backreference in a regular expression. Im working in a multprocess > > script so the first what i think is in an error in the multiprocess > > logic but what a sorprise!!! when arrived to this conclussion after > > some time debugging i see that: > > > import re > > aa = "zzz:xxx" > > re.sub(r'(zzz:).*',r'\1'+str(3333),aa) > > '[33' > > If you perform the addition you get r"\13333". How should the regular > expression engine interpret that? As the backreference to group 1, 13, ... > or 13333? It picks something completely different, "[33", because "\133" is > the octal escape sequence for "[": > > >>> chr(0133) > > '[' > > You can avoid the ambiguity with > > extra = str(number) > extra = re.escape(extra) > re.sub(expr r"\g<1>" + extra, text) > > The re.escape() step is not necessary here, but a good idea in the general > case when extra is an arbitrary string. > > Peter Aha!!! nice thanks i don't see that part of the re module documentation and it was in front of my eyes :(( like always its something silly jjj so thanks again and yes!! is a nice idea to escape the variable ;)
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