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Crimes with Python's Pattern Matching (2022)

Crimes with Python's Pattern Matching (2022)

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·August 21, 2025
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quotemstr

I've never understood why Python's pattern-matching isn't more general.

First, "case foo.bar" is a value match, but "case foo" is a name capture. Python could have defined "case .foo" to mean "look up foo as a variable the normal way" with zero ambiguity, but chose not to.

Second, there's no need to special-case some builtin types as matching whole values. You can write "case float(m): print(m)" and print the float that matched, but you can't write "case MyObject(obj): print(obj)" and print your object. Python could allow "..." or "None" or something in __match_args__ to mean "the whole object", but didn't.