Hi.
Example test.py:
class A():
def __add__(self, var):
print("I'm in A class")
return 5
a = A()
a+1
1+a
Execution:
python test.py
I'm in A class
Traceback (most recent call last):
File "../../test.py", line 7, in <module>
1+a
TypeError: unsupported operand type(s) for +: 'int' and 'instance'
So adding integer to class works fine, but adding class to integer fails.
I could not understand why it happens. In objects/abstact.c we have the
following function:
static PyObject *
binary_op1(PyObject *v, PyObject *w, const int op_slot)
{
PyObject *x;
binaryfunc slotv = NULL;
binaryfunc slotw = NULL;
if (v->ob_type->tp_as_number != NULL)
slotv = NB_BINOP(v->ob_type->tp_as_number, op_slot);
if (w->ob_type != v->ob_type &&
w->ob_type->tp_as_number != NULL) {
slotw = NB_BINOP(w->ob_type->tp_as_number, op_slot);
if (slotw == slotv)
slotw = NULL;
}
if (slotv) {
if (slotw && PyType_IsSubtype(w->ob_type, v->ob_type)) {
x = slotw(v, w);
if (x != Py_NotImplemented)
return x;
Py_DECREF(x); /* can't do it */
slotw = NULL;
}
x = slotv(v, w);
if (x != Py_NotImplemented)
return x;
Py_DECREF(x); /* can't do it */
}
if (slotw) {
x = slotw(v, w);
if (x != Py_NotImplemented)
return x;
Py_DECREF(x); /* can't do it */
}
Py_RETURN_NOTIMPLEMENTED;
}
When we adding class to integer we have both slotv and slotw. x = slotv(v, w);
-> returns Py_NotImplemented.
But in this case we should execute x = slotw(v, w); and function should be
completed in the same way as when we adding integer to class.
Can someone advise please where I mistake.
--
thanks,
Igor Vasilyev
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