How to rermove non-alphanumeric characters at the beginning or end of a string

Question

I have a list with elements that have unnecessary (non-alphanumeric) characters at the beginning or end of each string.

Ex.

\'cats--\'

Answer 1

To remove one or more chars other than letters, digits and _ from both ends you may use

re.sub(r'^\W+|\W+$', '', '??cats--') # => cats

Or, if _ is to be removed, too, wrap \W into a character class and add _ there:

re.sub(r'^[\W_]+|[\W_]+$', '', '_??cats--_')

See the regex demo and the regex graph:

See the Python demo:

import re
print( re.sub(r'^\W+|\W+$', '', '??cats--') )          # => cats
print( re.sub(r'^[\W_]+|[\W_]+$', '', '_??cats--_') )  # => cats