There are several reasons to use a group in a regular expression:
- to change the precedence (e.g.
do(g|or) will match 'dog' and 'door')
- to remember parenthesised part of the match in the case of capturing group
- to improve readability
In any case, having an empty group is most probably a mistake. Either it is a leftover after refactoring and should be removed, or the actual
parentheses were intended and were not escaped.
Noncompliant Code Example
r"foo()" # Noncompliant, will match only 'foo'
r"foo\(\)" # Matches 'foo()'