Python Regex char class

Question

Python 3

I have recently started reading regex and consider the following case :

If input is AB followed by C or D i want to replace it with EF

So, my char class is [CD] and it should be non-capturing .

Using the re.sub i come up with the following:

re.sub(r'AB(?:[CD])','EF',text)

When i run this code for input ABCZ i get EFZ

Thanks!

Answer 1

Non-capturing doesn't mean it's not included in the match. It just means it's not captured as a group (so you can't use backreferences like \\1 to refer to it).

If you want to specify that [CD] should follow but not be included in the match, you need to use a lookahead:

>>> re.sub(r'AB(?=[CD])','EF','ABCZ')
'EFCZ'