[docs] [issue17576] PyNumber_Index() is not int-subclass friendly (or operator.index() docos lie)

Barry A. Warsaw report at bugs.python.org
Sat Mar 30 01:39:42 CET 2013


Barry A. Warsaw added the comment:

On Mar 30, 2013, at 12:29 AM, Eric Snow wrote:

>Would it be okay to do a check on __index__ after the PyLong_Check()
>succeeds?  Something like this:
>
>    if (PyLong_Check(item) &&
>        item->ob_type->tp_as_number->nb_index == PyLong_Type.tp_as_number->nb_index) {
>        Py_INCREF(item);
>        return item;
>    }
>
>This is something Nick and I were talking about at the sprints regarding fast
>paths in the abstract API (for mappings and sequences in our case).

I think that would work, yes.  With this extra check, overriding __index__()
in the subclass should fail this condition and fall back to the
PyIndex_Check() clause.

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<http://bugs.python.org/issue17576>
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