What are decorators in Python

Decorators in Python are a design pattern that allows you to modify the behavior of a function or method without changing its source code. This is done by defining a decorator function that wraps the original function and modifies its behavior in some way. Decorators can be applied to functions, methods, and even classes.

Here’s an example of a decorator that counts the number of times a function is called:

def count_calls(func):
@functools.wraps(func)
def wrapper(*args, **kwargs):
wrapper.num_calls += 1
print(f”Call {wrapper.num_calls} of {func.__name__!r}”)
return func(*args, **kwargs)

wrapper.num_calls = 0
return wrapper

@count_calls
def say_hello(name):
print(f”Hello, {name}!”)

say_hello(“Alice”)
say_hello(“Bob”)
say_hello(“Charlie”)

Below is the result when the aforementioned is executed run this code:

Call 1 of ‘say_hello’
Hello, Alice!
Call 2 of ‘say_hello’
Hello, Bob!
Call 3 of ‘say_hello’
Hello, Charlie!

This shows that the say_hello function has been called 3 times.

In this example, count_calls is a decorator factory. It creates and returns a decorator function that wraps the original function and modifies its behavior. The decorator function (wrapper) is defined inside the decorator factory (count_calls). This allows the decorator to keep track of the number of times the function has been called, even across multiple invocations.

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