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pythonpython-typing

Python type hints: typing.Mapping vs. typing.Dict

I'm working on a python3 project where we use the typing module type hints throughout.

It seems that we use typing.Dict and typing.Mapping pretty much interchangeably.

Is there a reason to prefer one over the other?

Solution

  • typing.Dict should be used to indicate a literal dict type with support for element type hinting i.e. Dict[bytes, str].

    typing.Mapping is an object which defines the __getitem__, __len__, __iter__ magic methods.

    typing.MutableMapping is an object which defines same as Mapping but with __setitem__, __delitem__ magic methods as well.

    typing.Mapping et al. are based on the abc types in this table.