Python re.sub() is replacing the full match even when using non-capturing groups [duplicate]

Answer 1

The general solution for such problems is using a lambda in the replacement:

string = 'aBCDeFGH'

print(re.sub('(a)?([A-Z]{3})(e)?([A-Z]{3})', lambda match: '+%s+%s' % (match.group(2), match.group(4)), string))

However, as bro-grammer has commented, you can use backreferences in this case:

print(re.sub('(a)?([A-Z]{3})(e)?([A-Z]{3})', r'+\2+\4', string))