Python callable() built-in function

From the Python 3 documentation 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. Note that classes are callable (calling a class returns a new instance); instances are callable if their class has a call() method.

Introduction¶

In Python, the callable() function is a built-in function that can be used to determine if an object is callable, meaning it can be invoked as a function.

It returns True if the object passed to it is callable and False otherwise. For example, a function, a method, a class, a lambda function, and a generator are all callable objects in Python.

Here is an example of how you can use the callable() function:

>>> def my_function():
...     pass
...
>>> class MyClass:
...     def __call__(self):
...         pass
...
>>> x = 5
>>> y = my_function
>>> z = MyClass()
>>> a = lambda: None
>>>
>>> print(callable(x))
# False
>>> print(callable(y))
# True
>>> print(callable(z))
# True
>>> print(callable(a))
# True

In the above example, my_function is a function and it is callable, MyClass is a class and it is callable as well because it has a __call__ method, z is an instance of the class MyClass and it is also callable because it has a __call__ method and a is a lambda function which is callable.

The callable() function can be useful in situations where you need to determine if an object can be invoked as a function, such as when you are working with callbacks or other types of function pointers.