Syntax
object.__call__(self[, args...])The Python __call__ method makes a class callable, so you can call objects of the class like a normal function. For example, if you define __call__(self) on an object x of class X, you can call it like so: x(). The return value of the called object is the return value of the __call__() method.
We call this a “Dunder Method” for “Double Underscore Method” (also called “magic method”). To get a list of all dunder methods with explanation, check out our dunder cheat sheet article on this blog.
💡 Note: Formally, calling x(arg1, arg2, ...) translates to type(x).__call__(x, arg1, ...) whereas the type() built-in function determines the class (type) of x.
Minimal Example __call__
The following code snippet makes a custom class Person callable by providing an implementation of the magic method __call__() that takes two arguments:
self– a reference to the object itself. This is automatically passed into the function by Python—you don’t need to provide the argument yourself.other– an additional argument (e.g., a string) to provide a custom greeting.
With this implementation, we can now create a callable object alice and call it like so: alice().
class Person:
def __call__(self, other):
return f'Hi {other}'
alice = Person()
print(alice('Bob'))
# Hi Bob
Background callable
Python’s built-in callable(object) returns True if you could call the object argument like a function with the trailing parentheses in object().
You can make any object callable by implementing the instance’s __call__() method.
For example, callable(callable) returns True because callable is a function object. But callable(3) returns False because an integer is not a function you can call.
>>> callable(callable) True >>> callable(3) False
You can learn more about the function in our detailed blog guide:
References:
Where to Go From Here?
Enough theory. Let’s get some practice!
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