I've run into a problem with ExtensionClass which I believe can
only be fixed by modifying Python. I will try to explain.
I have an ExtensionClass which defines __cmp__. Depending on the
objects being compared, the __cmp__ method may never be called.
This is due to code in object.c that looks like this:
if (PyInstance_Check(v) || PyInstance_Check(w)) {
try to use use __cmp__ method
}
else {
try number coerce and fall back on type name comparison
}
Extension classes can never pass the PyInstance_Check predicate.
I've searched for all occurances of PyInstance_Check in the 2.0
source. In many places that PyInstance_Check occurs a more
general "is this an instance-like type" check would seem to be
more suitable.
Here is my proposal:
* Define a new type flag Py_TPFLAGS_INSTANCE.
* Create a new predicate Py_IsInstance which checks for this
flag.
* Set this flag on PyInstance_Type.
* Replace most occurances of PyInstance_Check with
Py_IsInstance.
Extension types (like ExtensionClass) can then define the type
flag Py_TPLAGS_INSTANCE and be treated as an instance type by the
Python interpreter. This should make it quite a bit easier to make
extension types behave like "real" classes.
Comments?
Neil
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