from contextlib import contextmanager
import re

@contextmanager
def assign_match(regex, string):
    match = re.match(regex, string)
    if match:
        yield match.groups()

for i in range(3):
    with assign_match('(abc)(def)', 'ABCDEF') as a:
#    for a in assign_match('(abc)(def)', 'abcdef'):
        print(a)
        continue
    print(i)