It is unreliable to use hasattr(object, '__call__') to check if an object is callabe as it can give wrong results if object implements custom __getattr__ or its __call__ is itself not callabe. It is recommended to use the callable built-in instead.

Here's an example:

In [1]: class FooBar:
    ...:     def __init__(self):
    ...:         self.foo = "Foo"
    ...:         self.bar = "Bar"
    ...:
    ...:     def __getattr__(self, key):
    ...:         return key
    ...:

In [2]: instance = FooBar()

When hasattr is used to check if instance is callable, it return True

In [3]: hasattr(instance, '__call__')
Out[3]: True

But when checked using the callable built-in, it returns False

In [4]: callable(instance)
Out[4]: False

When instance is called, here's the traceback:

In [5]: instance()
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-23-5dd8ea036ab8> in <module>
----> 1 instance()

TypeError: 'FooBar' object is not callable

QuackatronHQ / Gigarepo

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