Python C API, How to call base type method from subtype?

Question

I created a subtype from one existing Python type with C API by following this guide Python C API Defining New Types

I overridden one base type's method by registering the new method thanks to tp_methods attribute of the new PyTypeObject. This is working fine.

But, the code must also be able to execute the base type method (the one that has been overrided. I can not find documentation on how to do it.

Any idea are welcome, Thanks

Answer 1

I think there's 2.5 options, in order of complexity:

1. Just find the C function that defines it. When using the C API the chances are you're inheriting from a known class that is implemented in C. In that case you'd track down the C function used for the method and call that.

2. Get the class from the object, the base from the class:

   a. PyObject* baseclass = self->ob_type->tp_base;

   b. Use the C API equivalent of super():

   PyObject* baseclass = PyObject_CallFunctionObjArgs(&PySuper_Type,self->ob_type,self,NULL);

   With the base found you can then use the C API equivalent of getattr to get the relevant function:

.

/* check baseclass against null */
PyObject* func = PyObject_GetAttrString(baseclass,"function_name");
/* check func is not null */
PyObject* result = PyObject_CallFunctionObjArgs(self,other_arguments..., NULL); /* adjust arguments here */
Py_DECREF(func);
// decref result?

You can use a different method of calling it but you need to make sure you pass self with the arguments.

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Option 2b is probably most flexible since it should work when multiple bases are defined through the tp_bases.