I have a simple function that should output a prefix based on a pattern or None if it does not match. Trying to do a walrus it does not seem to work. Any idea?
import re def get_prefix(name): if m := re.match(f'^.+(\d\d)-(\d\d)-(\d\d\d\d)$', name) is not None: return m.group(3) + m.group(2) + m.group(1) get_prefix('abc 10-12-2020') Traceback
Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 3, in get_prefix AttributeError: 'bool' object has no attribute 'group' 1 Answer
You're setting m to re.match(f'^.+(\d\d)-(\d\d)-(\d\d\d\d)$', name) is not None, which is a boolean.
You probably mean
if (m := re.match(f'^.+(\d\d)-(\d\d)-(\d\d\d\d)$', name)) is not None: But you don't need is not None here anyway. Matches are truthy and None is falsey. So you just need:
if m := re.match(f'^.+(\d\d)-(\d\d)-(\d\d\d\d)$', name): (Arguably it's better practice to use () whenever you're using an assignment expression, to make clear what's being assigned.)
See PEP572#Relative precedence of :=
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