[Cython] callable() optimization
Vitja Makarov
vitja.makarov at gmail.com
Wed May 9 10:21:54 CEST 2012
2012/5/9 Stefan Behnel <stefan_ml at behnel.de>:
> Vitja Makarov, 09.05.2012 09:43:
>> 2012/5/9 Stefan Behnel <stefan_ml at behnel.de>:
>>> Vitja Makarov, 08.05.2012 13:27:
>>>> I've noticed regression related to callable() optimization.
>>>>
>>>> https://github.com/cython/cython/commit/a40112b0461eae5ab22fbdd07ae798d4a72ff523
>>>>
>>>> class C:
>>>> pass
>>>> print callable(C())
>>>>
>>>> It prints True optimized version checks ((obj)->ob_type->tp_call !=
>>>> NULL) condition that is True for both class and instance.
>>>>
>>>>>>> help(callable)
>>>> callable(...)
>>>> callable(object) -> bool
>>>>
>>>> Return whether the object is callable (i.e., some kind of function).
>>>> Note that classes are callable, as are instances with a __call__() method.
>>>
>>> Ah, right - old style classes are special cased in Py2.
>>>
>>> I'll make this a Py3-only optimisation then.
>>>
>>
>> I don't see difference between py2 and py3 here:
>>
>> Python 3.2.3 (default, May 3 2012, 15:51:42)
>> [GCC 4.6.3] on linux2
>> Type "help", "copyright", "credits" or "license" for more information.
>> >>> class Foo: pass
>> ...
>> >>> callable(Foo())
>> False
>> >>>
>>
>> There is PyCallable_Check() CPython function:
>>
>> int
>> PyCallable_Check(PyObject *x)
>> {
>> if (x == NULL)
>> return 0;
>> if (PyInstance_Check(x)) {
>> PyObject *call = PyObject_GetAttrString(x, "__call__");
>> if (call == NULL) {
>> PyErr_Clear();
>> return 0;
>> }
>> /* Could test recursively but don't, for fear of endless
>> recursion if some joker sets self.__call__ = self */
>> Py_DECREF(call);
>> return 1;
>> }
>> else {
>> return x->ob_type->tp_call != NULL;
>> }
>> }
>
> That's the Py2 version. In Py3, it looks as follows, because old-style
> "instances" no longer exist:
>
> """
> int
> PyCallable_Check(PyObject *x)
> {
> if (x == NULL)
> return 0;
> return x->ob_type->tp_call != NULL;
> }
> """
>
> That's what I had initially based my optimisation on.
>
Ok, so why don't you want to use PyCallable_Check() in all cases?
--
vitja.
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