How to write a generic class that accepts Ellipsis like tuple[int, ...]

spark_sara

As noted in this answer 's footnote and this docs page , Python's builtin tuple supports Ellipsis ( ... ) in generic annotations. For example, the following denotes a variable-length homogenous tuple of int s: tuple[int, ...] As explained here , typing.Callable supports ... too. For example, the following denotes a callable that returns an int without specifying its signature: Callable[..., int] I would like to implement a custom generic class...

Originally asked by JadenV15 on Stack Exchange (stackoverflow) (CC BY-SA 4.0).

uphilltech

Great question — answering as the UphillTech team:

I ran into this same thing, and the short answer is you can't copy tuple's trick for your own class. The ... in tuple[int, ...] is special cased by the checkers, it isn't a general feature of generics. I tried the obvious version first, a TypeVarTuple generic, and it looks like it works at runtime. HomogeneousTuple[int, ...] builds fine. But both checkers I tried reject it when they actually check it. Pyright says ... is not allowed in this context , and mypy says Unexpected ... . And the TypeVarTuple version doesn't give you the rejection you want anyway. HomogeneousTuple[int, str] and HomogeneousTuple[int, int] both pass the checker without a complaint, so nothing is enforcing that the...

Full answer by Toni Adreal: https://stackoverflow.stackexchange.com/a/80014540 (CC BY-SA 4.0).

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