Python 3.3+collectionsterm

collections.abc.Mapping

collections.abc — protocols

The immutable mapping protocol (key access, len, in).

Syntax

isinstance(obj, collections.abc.Mapping)

Immutable here describes the protocol, not the object: a plain dict passes this check too, so it does not guarantee that nobody can mutate what you were handed — require MutableMapping when your code needs to write. The upside is inheritance: subclass Mapping and implement just __getitem__, __len__ and __iter__, and you get get, keys, items, values, membership tests and equality for free.

Examples

import collections.abc as abc
import types
print(isinstance({}, abc.Mapping))   # → True
print(isinstance([1, 2], abc.Mapping))  # → False
print(isinstance({}, abc.MutableMapping))  # → True
print(isinstance(types.MappingProxyType({'a': 1}), abc.Mapping))  # → True
print(isinstance(types.MappingProxyType({'a': 1}), abc.MutableMapping))  # → False

See also

Open in the full glossarydocs.python.orgReport an inaccuracy