Can you explain what the decorator pattern is in Python and how it is used?

The decorator pattern in Python is a way to dynamically extend the functionality of functions or methods without changing their original code. A decorator is a function that takes another function and returns a new function with additional behavior.

Here's an example of a simple decorator that outputs the execution time of a function:

import time

def timer(func):
    def wrapper(*args, **kwargs):
        start = time.time()
        result = func(*args, **kwargs)
        end = time.time()
        print(f"Execution time of {func.__name__}: {end - start:.4f} seconds")
        return result
    return wrapper

@timer
def some_function():
    time.sleep(1)

some_function()

Here, @timer is syntactic sugar for some_function = timer(some_function). Decorators are widely used for logging, access control, caching, and other aspects, separating additional logic from the main function.