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ast.In

operators

The marker for the comparison in in an ast tree: it sits in Compare.ops and has no fields.

Syntax

ast.In()

'x in y' is a comparison (Compare), not a call; 'x not in y' is a single NotIn operator, while 'not x in y' is UnaryOp(Not) wrapping a Compare with In: same meaning, different trees. The in keyword of a for header is not an In operator at all — it is part of the For node. Compare marker nodes by type (isinstance), not with ==: ast nodes have no __eq__, so ast.In() == ast.In() is False.

Examples

import ast
print(type(ast.parse('x in y', mode='eval').body.ops[0]).__name__)  # → In
print(type(ast.parse('x not in y', mode='eval').body.ops[0]).__name__)  # → NotIn
print(type(ast.parse('not x in y', mode='eval').body).__name__)  # → UnaryOp

See also

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