Determine if __getattr__ is method or attribute call

You cannot tell how an object is going to used in the __getattr__ hook, at all. You can access methods without calling them, store them in a variable, and later call them, for example.

Return an object with a __call__ method, it'll be invoked when called:

class CallableValue(object):
    def __init__(self, name):
        self.name = name
    def __call__(self, *args, **kwargs):
        print "Lo, {} was called!".format(self.name)

class Bar(object):
    def __getattr__(self, name):
        return CallableValue(name)

but instances of this will not be the same thing as a string or a list at the same time.

Demo:

>>> class CallableValue(object):
...     def __init__(self, name):
...         self.name = name
...     def __call__(self, *args, **kwargs):
...         print "Lo, {} was called!".format(self.name)
... 
>>> class Bar(object):
...     def __getattr__(self, name):
...         return CallableValue(name)
... 
>>> b = Bar()
>>> something = b.test_method
>>> something
<__main__.CallableValue object at 0x10ac3c290>
>>> something()
Lo, test_method was called!