For context this respects the descriptor protocol:

>>> a()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 4, in __call__
AttributeError: go away

Mind you, this is legal use:

>>> class B:
...  @property
...  def __call__(self):
...   return lambda: 1
...
>>> b = B()
>>> b()
1