Callable assertion?

[Gonçalo Rodrigues]

On Sun, 05 Oct 2003 10:20:11 -0400, Roy Smith <roy at panix.com> wrote:

>In article <wMOdnYxfQN0hux2iRTvUqg at speakeasy.net>,
> "A.M. Kuchling" <amk at amk.ca> wrote:
>
>> On Sun, 05 Oct 2003 08:55:45 -0400, 
>> 	Roy Smith <roy at panix.com> wrote:
>> > the right thing to do, or is there something cleaner?  Will that work 
>> > for all callable values of param, regardless if it's a static function, 
>> > class method, built-in, etc?
>> 
>> There's a callable(param) built-in function, dating back to Python 1.2.
>> 
>> --amk
>
>Ah.  That's exactly what I was looking for!  The docs say:
>
>"Return true if the object argument appears callable, false if not.  If 
>this returns true, it is still possible that a call fails,  but if it is 
>false, calling object will never succeed."
>
>What does "appears callable" mean?  Under what circumstances would 
>callable(foo) return True, yet foo() would fail?


An extreme and artificial example:

>>> class FakeCallable(object):
... 	def __call__(self, *args, **kwargs):
... 		raise TypeError("My only purpose in life is to trick
the Python interpreter.")
... 
>>> a = FakeCallable()
>>> callable(a)
True
>>> a()
Traceback (most recent call last):
  File "<interactive input>", line 1, in ?
  File "<interactive input>", line 3, in __call__
TypeError: My only purpose in life is to trick the Python interpreter.
>>> 

Best,
G. Rodrigues