Python 3.10+astterm

ast.MatchStar

pattern matching

The *name pattern inside a sequence case: it captures the remaining elements as a list; for *_ the name field is None.

Syntax

ast.MatchStar(name)

It appears only inside a MatchSequence and at most once per pattern. The captured rest is always a list, even when a tuple was matched. '*_' skips elements without binding: name=None, and no variable _ is created. The double star in a mapping pattern is not a MatchStar but the rest field of MatchMapping.

Examples

import ast
p = ast.parse('match x:\n    case [h, *t]: pass\n    case [*_]: pass').body[0]
print([q.name for q in p.cases[0].pattern.patterns])  # → ['h', 't']
print(p.cases[1].pattern.patterns[0].name)  # → None

match (1, 2, 3):
    case (first, *rest):
        print(first, rest)  # → 1 [2, 3]

See also

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