When I compile and match, for example:
pattern = re.compile(r"""    ([a-z]|\d)+$         # ends with letter or number only    """, re.VERBOSE | re.IGNORECASE)
print(re.match(pattern, 'abc'))

result is correct:
<_sre.SRE_Match object; span=(0, 3), match='abc'>

but then I use the same pattern with another string:
print(re.match(pattern, 'abc.fds'))

result is: 
None

I tried to reformulate the pattern to the same, for example:
pattern = re.compile(r"""    (a|b|c|d|e|f|g|h|i|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z|\d)+$         # ends with letter or number only    """, re.VERBOSE | re.IGNORECASE)

or to:
pattern = re.compile(r"""    [a-z\d]+$         # ends with letter or number only    """, re.VERBOSE | re.IGNORECASE)

or to:

pattern = = re.compile(r"""    ([a-z]|\d)+$         # ends with letter or number only    """, re.VERBOSE | re.IGNORECASE)

but the result is all the time the same - None
And еhat is the double strange for the last three pattern - None is result also for 
print(re.match(pattern, 'abc'))

I checked this patterns on the site regex101.com
and all of them should work good and right
It's achtung!

re.match only matches at the start of the string. If you use re.search instead, you will get the results you are expecting.