Python 3.10+astterm

ast.MatchValue

pattern matching

A value pattern in a case: a literal or a dotted name (case 200, case Color.RED); compared with the subject using ==.

Syntax

ast.MatchValue(value)

The main match trap: a bare name is not a value. 'case RED:' yields not a MatchValue but a MatchAs — a capture that matches anything and rebinds RED; a name becomes a value only when dotted, 'case Color.RED:'. None, True and False are not MatchValue either but MatchSingleton, because they are compared with is.

Examples

import ast
src = 'match x:\n    case 200: pass\n    case Color.RED: pass\n    case RED: pass'
cases = ast.parse(src).body[0].cases
print([type(c.pattern).__name__ for c in cases])  # → ['MatchValue', 'MatchValue', 'MatchAs']

See also

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