I'm trying to write a descriptor (similar to the EiffelDescriptor example in the Demo directory). However, I noticed an odd behavior that descriptors written in pure Python mask the underlying object they are wrapping, whereas the descriptors written in C do not.
For example, taking the code from http://users.rcn.com/python/download/Descriptor.htm which implements what one would think is a straightforward implementation: class ClassMethod(object): "Emulate PyClassMethod_Type() in Objects/funcobject.c" def __init__(self, f): self.f = f def __get__(self, obj, klass=None): if klass is None: klass = type(obj) def newfunc(*args): return self.f(klass, *args) return newfunc class MyClass(object): def c_method_1(k, foo): "some docstring" print 'c_method_1: %r %r' % (k, foo) c_method_1 = ClassMethod(c_method_1) def c_method_2(k, foo): "some docstring" print 'c_method_2: %r %r' % (k, foo) c_method_2 = classmethod(c_method_2) You can see that the Python version does not behave the same as the C version: >>> print MyClass.c_method_1.__doc__ None >>> print MyClass.c_method_2.__doc__ some docstring I have seen some people manually assign the __doc__ attribute to match the method they are wrapping (above in the __get__ method it would be newfunc.__doc__ = self.f.__doc__ before the return). However, this extends further into introspection: >>> import inspect >>> print inspect.getargspec(MyClass.c_method_1) ([], 'args', None, None) >>> print inspect.getargspec(MyClass.c_method_2) (['k', 'foo'], None, None, None) SO, my question is, is it possible to make a simple descriptor in Python that has the same behavior as one implemented in C? Or, at least a way that does not require a very large amount of emulation code. ;) -Eric -- http://mail.python.org/mailman/listinfo/python-list
