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'

Compliant Solution

r"foo\(\)" # Matches 'foo()'