isinstance()

[Jon Ribbens]

On 2023-08-02, dn <PythonList at DancesWithMice.info> wrote:
> Can you please explain why a multi-part second-argument must be a tuple 
> and not any other form of collection-type?

The following comment may hold a clue:

    if (PyTuple_Check(cls)) {
        /* Not a general sequence -- that opens up the road to
           recursion and stack overflow. */

https://github.com/python/cpython/blob/main/Objects/abstract.c#L2684

Plus an almost total lack of demand for change I should think.