all Python 3operatorfunction

operator.contains

sequences

Membership test: b in a (note the argument order).

Syntax

operator.contains(a, b)

The argument order is the reverse of b in a: container first, then the item. That makes partial(operator.contains, allowed) a ready predicate "x is in allowed" for filter. For a dict it checks keys, not values: contains({'a': 1}, 1) is false. Speed depends on the container: set and dict answer almost instantly, a list is scanned.

Examples

import operator
print(operator.contains([1, 2, 3], 2))   # → True
print(operator.contains('python', 'th'))   # → True
print(operator.contains({'a': 1}, 'a'))   # → True
print(operator.contains({'a': 1}, 1))   # → False
print(operator.contains(2, [1, 2, 3]))   # → TypeError

See also

Common errors

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