Does re.compile change pattern functionality?

November 9, 2021

For some reason, when I re.compile a list of unioned regex patterns it seems as though some patterns work and some do not. Can’t figure out the issue here though. Any guidance appreciated.

import re

creditcard_pattern  = re.compile(r'''(
                    (CREDIT\s?CA?RD)|
                     ((CARD|\bCC\b).*PA?YME?N?T?)|
                    (APPLECARD)|
                    WELLS FARGO.*(CARD|CC)|
                    (CITI.*(C?R?E?D?I?T CA?R?D))|
                    (CAPITAL ONE)|
                    AMERICAN EXPRESS|
                    (DISCOVER.*(?!.*1BANK))|
                    AMER?I?C?A?N?\s?E?XP?R?E?S?S?|
                    CHASE.*CARD|
                    (BA?N?K.*AME?RI?C?A?.*PMT)|
                    AMEX|
                    CITICORP CHOICE|
                    CITI (CARD|AUTO|PAYMENT)|
                    VISA PLATINUM|
                    BARCLAY.*CARD|
                    USAA FSB.*ONLINE PMT|
                    CITIBANK.*ONLINE PMT
                    )
               ''', flags=re.I | re.X )

Testing:


if creditcard_pattern.search('CARD PYMT'):
    print('found')
    #>> found

if creditcard_pattern.search('BARCLAY CARD'):
    print('found')
    #>> found

if creditcard_pattern.search('WELLS FARGO CARD'):
    print('found')
    #>> not found

if creditcard_pattern.search('CAPITAL ONE'):
    print('found')
    #>> not found

When testing the patterns in https://regexr.com/ my patterns seem to work as expected…

>Solution :

The documentation for re.X states:

Whitespace within the pattern is ignored, except when in a character
class, or when preceded by an unescaped backslash, or within tokens
like *?, (?: or (?P<…>.

So you could escape the single space in ‘CAPITAL ONE’, the corresponding line in your regex becomes: