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If parentheses are not added, the returned result is the groups matched by regular expressions;
If parentheses are added, all groups will be returned, including unmatched groups.
The official document is very clear, I just translated it for you.
Explanation in python3-cookbook
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If parentheses are not added, the returned result is the groups matched by regular expressions;
If parentheses are added, all groups will be returned, including unmatched groups.
The official document is very clear, I just translated it for you.
Explanation in python3-cookbook