Re: [Python-Dev] PyObject_IsInstance is dangerous

Serhiy Storchaka wrote:

PyObject_IsInstance is not safe when used to check if the object is an instance of specified builtin type.

The __class__ attribute can be modified and PyObject_IsInstance() can return true if the object has not layout compatible with specified structure.

Code that requires a particular C layout should be using PyObject_TypeCheck, not PyObject_IsInstance. -- Greg