[Python-3000] Could isinstance/issubclass overriding be dangerous?

[Phillip J. Eby]

At 06:27 PM 4/30/2007 +1200, Greg Ewing wrote:
>So can we please have another couple of functions that just
>do a simple, reliable concrete type test?

I believe the operation you're looking for (i.e., C-level layout 
compatibility) is:

C in type.__mro__.__get__(type(x))

or in Pyrex:

C in (((PyTypeObject *) type(x)).tp_mro)