On 11/08/2014 02:31 PM, Gregory Ewing wrote:
Seems to depend on how you get hold of the object you're
inspecting the signature of. I did an experiment:
class C(object):
@property
def __call__(self):
return self.call
def f(x, y):
print("Called f with %s, %s" % (x, y))
c = C()
c.call = f
c(17, 42)
prints:
Called f with 17, 42
This works too:
import inspect
print(inspect.getargspec(c.__call__))
prints:
ArgSpec(args=['x', 'y'], varargs=None, keywords=None, defaults=None)
But
print(inspect.getargspec(c))
doesn't work:
TypeError: <__main__.C object at 0x479250> is not a Python function
(BTW, I'm actually surprised that this technique makes c callable.
There must be more going on that just "look up __call__ in the class
object", because evaluating C.__call__ just returns the descriptor
and doesn't invoking the descriptor mechanism.)
Looks like you found a bug in inspect.getargspec.
And the thing going on is the normal python behavior (in __getattribute__, I believe) of examining the returned
attribute to see if it is a descriptor, and if so invoking it.
--
~Ethan~
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