I want to extract a certrain string from a path. The wanted string is always preceded by either \0_ASW\ or \10_BSW\ words. Additionally, the sought string consists of only letters and numbers.
So for example from the following 3 paths I want to extract strings Mod2000, ModA and ModB:
C:\MyPath\0_ASW\Mod2000
C:\MyPath\10_BSW\ModA\SubDir
C:\MyPath\10_BSW\ModB
For that I have written a regex using Positive Lookbehind:
\\(?<=(0_ASW|10_BSW)\\)([A-Za-z0-9] )
With this regex the 2nd group matches the sought string correctly and I am able to compile the regex in .NET(C#) without any errors. However, once I try to compile it in Python I get the following Regex Error: A lookbehind assertion has to be fixed width
From my understanding, the two words in the positive lookbehind, i.e. 0_ASW and 10_BSW ought to have the fixed length. The error is not clear to me because both words have a fixed length of 4 and 5 characters, respectively. If I try to make those 2 strings to have equal length, e.g. 3 character strings ASW and BSW, the regex compiles without the above error.
\\(?<=(ASW|BSW)\\)([A-Za-z0-9] )
How do I fix this regex so that it compiles in Python as well?
You can find the demos here:
https://regex101.com/r/qfwfJJ/1
https://regex101.com/r/zAVk5Z/1
CodePudding user response：
You could also use a non-capturing group:
\\(?:0_ASW|10_BSW)\\(\w )
https://regex101.com/r/hYCRJf/1
If the regex matches, you'll get the desired string in group(1).
CodePudding user response：
\\((0_ASW|10_BSW)\\)([A-Za-z0-9] )