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

python python-3.x type-hinting
stacksonstacks picture stacksonstacks · Sep 24, 2018 · Viewed 12.4k times · Source

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?

Answer

stacksonstacks picture stacksonstacks · Sep 24, 2018

Managed to answer this myself.

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

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