Where is the `dict_keys` (and `dict_values` (and `dict_items`)) class?

[George-Ogden]

How can I check if an object is a dict_keys() in Python?

My current options are:

1. seems bad style:

dict_keys = type(dict().keys())
is_dict_keys = isinstance(foo, dict_keys)

2. overzealously matches:

from collections.abc import KeysView
is_dict_keys = isinstance(foo, KeysView)

There's no way to import this from the types library and there's no documentation about it in the Dictionary view objects section of the documentation.
Is there a better way to do this? Is dict_keys intentionally excluded from the documentation?

[George-Ogden]

I also notice:

## views ##
dict_keys = type({}.keys())
dict_values = type({}.values())
dict_items = type({}.items())

in the current collections.abc library

[JelleZijlstra]

As you noticed, the types are present in the collections.abc module as an implementation detail, but that shouldn't be relied upon. In user code, it's also possible to retrieve the types using the same technique collections.abc uses.

What's the use case for needing these types in user code? If there's a good justification, we could add them to the types module (e.g., as types.DictKeysType), but I am not sure what code needs to specifically handle the concrete dict_keys type and not other implementations of the KeysView ABC.

[terryjreedy]

I am included to close this as 'nothing more needed'. Either 1 or 2 look fine to me. There are about 20 of these implementation classes left out of types (and likely more not listed in .abc and I think they should continue to be omitted.