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Building Robust Object-Oriented Python Applications and Libraries

Callable Objects

Explore how to make instances of Python classes callable by defining the __call__ method. Understand the difference between functions and callable objects, and learn how callable objects can maintain state to optimize performance and functionality.

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Overview

Just as functions are objects that can have attributes set on them, it is possible to create an object that can be called as though it were a function. Any object can be made callable by giving it a __call__() method that accepts the required arguments.

Example

Let’s make our Repeater class (Repeater_2), from the timer example, a little easier to use by making it a callable, as follows:

Python 3.10.4
class Repeater_2:
    def __init__(self) -> None:
        self.count = 0
        
    def __call__(self, timer: float) -> None:
        self.count += 1
        format_time(f"Called Four: {self.count}")
...