Python 3.10+astterm

ast.MatchSequence

pattern matching

A sequence pattern case [a, b] or case (a, b): patterns are the element patterns, one of which may be a MatchStar.

Syntax

ast.MatchSequence(patterns)

Square and round brackets give the same node and match list and tuple alike — 'case (a, b)' also catches [1, 2]. Strings, bytes and bytearray never match a sequence pattern, although they are sequences: 'case [a, b]' does not match 'ab'. Without a * the length must match exactly.

Examples

import ast
p = ast.parse('match x:\n    case (a, *rest): pass').body[0].cases[0].pattern
print(type(p).__name__, [type(q).__name__ for q in p.patterns])  # → MatchSequence ['MatchAs', 'MatchStar']

def f(v):
    match v:
        case (a, b):
            return 'pair'
    return 'no'
print(f([1, 2]), f('ab'))  # → pair no

See also

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