Python 3.10+astterm

ast.MatchOr

pattern matching

An alternative pattern case 1 | 2 | 3: patterns is the list of options; the first that matches, left to right, wins.

Syntax

ast.MatchOr(patterns)

Every alternative must bind the same set of names: 'case [x] | (x, _)' is legal, while 'case [x] | 1' is a SyntaxError raised by the compiler: ast.parse builds that tree without complaint. The | here is not bitwise OR: no BinOp(BitOr) appears inside a case, and 'case Color.R | Color.G' works through MatchValue nodes inside a MatchOr.

Examples

import ast
p = ast.parse('match c:\n    case 1 | 2 | 3: pass').body[0].cases[0].pattern
print(type(p).__name__, [q.value.value for q in p.patterns])  # → MatchOr [1, 2, 3]

import ast
try:
    compile(ast.parse('match v:\n    case [x] | 1: pass'), '<m>', 'exec')
except SyntaxError as e:
    print(type(e).__name__)  # → SyntaxError

See also

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