collections.namedtuple() creates a tuple subclass, and as a subclass it inherits all tuple methods, including __class_getitem__.
The __new__ method has been overridden in a named tuple class. It no longer accept an iterator of arbitrary length. The named tuple has fixed number of elements, and the constructor accept fixed number of arguments (some may be optional).
But the __class_getitem__ is inherited from tuple. It allows to specialize the named tuple type with arbitrary number of arguments.
Point2D = namedtuple('Point2D', 'x y label')
Point2D[int, int, str]
Point2D[int, str]
Point2D[int, ...]It looks confusing at best. A named tuple is not a general tuple, it cannot have an arbitrary number of items.
There are two options:
- Forbid subscription of types created by
namedtuple(). If you want to add type annotations, use typing.NamedTuple.
- Add
__class_getitem__ which checks that the number of types corresponds to the size of the named tuple.
@rhettinger
collections.namedtuple()creates atuplesubclass, and as a subclass it inherits alltuplemethods, including__class_getitem__.The
__new__method has been overridden in a named tuple class. It no longer accept an iterator of arbitrary length. The named tuple has fixed number of elements, and the constructor accept fixed number of arguments (some may be optional).But the
__class_getitem__is inherited fromtuple. It allows to specialize the named tuple type with arbitrary number of arguments.It looks confusing at best. A named tuple is not a general tuple, it cannot have an arbitrary number of items.
There are two options:
namedtuple(). If you want to add type annotations, usetyping.NamedTuple.__class_getitem__which checks that the number of types corresponds to the size of the named tuple.@rhettinger