callable

In Python, a callable is any object that you can call like a function. This means you can use parentheses () to invoke the object and possibly pass arguments to it.

Functions, methods, and classes are callable. Calling a class creates a new instance. However, other objects can be made callable by implementing the .__call__() special method. This method allows you to create objects that behave like functions.

You can check if an object is callable using the built-in callable() function, which returns True if the object appears callable and False otherwise. A True result doesn’t guarantee that a call will succeed, but a False result means the call will always fail.

Understanding the concept of callables is essential when working with higher-order functions, decorators, and any Python feature that requires passing around functions or function-like objects.

class Adder:
    def __init__(self):
        self.value = 0

    def __call__(self, value):
        self.value += value
        return self.value

# Usage
adder = Adder()
adder(10)  # Output: 10
adder(10)  # Output: 20
adder(10)  # Output: 30

Related Resources

Tutorial

Python's .__call__() Method: Creating Callable Instances

In this tutorial, you'll learn what a callable is in Python and how to create callable instances using the .__call__() special method in your custom classes. You'll also code several examples of practical use cases for callable instances in Python.

intermediate python

For additional information on related topics, take a look at the following resources:

• Create Callable Instances With Python's .__call__() (Course)
• Primer on Python Decorators (Tutorial)
• Python Built-in Functions: A Complete Guide (Tutorial)
• Python's .__call__() Method: Creating Callable Instances (Quiz)
• Python Decorators 101 (Course)
• Primer on Python Decorators (Quiz)
• Exploring Python's Built-in Functions (Course)
• Python Built-in Functions: A Complete Guide (Quiz)