python re.sub replace number in match string

Question

Replacing numbers in a string after the match.

t = 'String_BA22_FR22_BC'
re.sub(r'FR(\d{1,})','',t)

My desired output would be String_BA22_FR_BC

Answer 1

You are replacing what you match (in this case FR22) with an empty string.

Another option is to use a positive lookbehind an then match 1+ digits adn replace that match with an empty string:

(?<=FR)\d+

Regex demo | Python demo

For example:

re.sub(r'(?<=FR)\d+','',t)

Answer 2

You may use

re.sub(r'FR\d+','FR',t)

Alternatively, you may capture the part you need to keep with a capturing group and replace with \1 backreference:

re.sub(r'(FR)\d+', r'\1', t)
         ^--^- >>>----^

See the Python demo

A capturing group approach is flexible as it allows patterns of unlimited length.