Subclassing typing.NamedTuple an inheriting from a mixin class does not work. It does work for collections.namedtuple, and can be worked around by modifying typing.NamedTupleMeta: >>> import collections >>> import typing >>> >>> >>> class Mixin: ... def mixin(self): ... return "mixin" ... >>> >>> class CollectionsNamedTuple(Mixin, collections.namedtuple('CollectionsNamedTuple', [ ... "a", ... "b", ... ])): ... pass ... >>> >>> class TypingNamedTuple(Mixin, typing.NamedTuple): ... a: str ... b: str ... >>> >>> class NamedTupleMeta(typing.NamedTupleMeta): ... def __new__(cls, typename, bases, ns): ... cls_obj = super().__new__(cls, typename + '_nm_base', bases, ns) ... bases = bases + (cls_obj,) ... return type(typename, bases, {}) ... >>> >>> class FixedTypingNamedTuple(Mixin, metaclass=NamedTupleMeta): ... a: str ... b: str ... >>> >>> cnt = CollectionsNamedTuple("av", "bv") >>> tnt = TypingNamedTuple("av", "bv") >>> ftnt = FixedTypingNamedTuple("av", "bv") >>> >>> cnt.mixin() 'mixin' >>> ftnt.mixin() 'mixin' >>> tnt.mixin() Traceback (most recent call last): File "<stdin>", line 1, in <module> AttributeError: 'TypingNamedTuple' object has no attribute 'mixin'

Hm, it looks like we can support this. I however don't think the proposed "patch" is the right way to fix it, since this makes the implementation with and without a mixin quite different. Also I am not sure I will have time to work on this in the nearest month.

 New changeset a94e6272f16381349dbed74cdb738ec8ae23b4fe by Serhiy Storchaka in branch 'master': bpo-36517: Raise error on multiple inheritance with NamedTuple (GH-19363) https://github.com/python/cpython/commit/a94e6272f16381349dbed74cdb738ec8ae23b4fe 

The patch PR blocks out a useful idiom: generic Nametuple >>> class LLNode(NamedTuple, Generic[T]): ... value :T ... next: Optional[LLNode[T]] I put forward that, at the least, NamedTuple should accept do-nothing bases like Generic.