Decorators

Decorators

A decorator is a function that extends the functionality of another function without explicitly modifying it. It takes a function as an argument, adds extra behavior within a nested “wrapper” function, and then returns the wrapper. This pattern is commonly used for tasks like logging, timing, or authentication.

The @ syntax is a shortcut for applying a decorator. For example, @timer is equivalent to calling slow_function = timer(slow_function). The nested wrapper function ensures that the original function is called with its arguments (*args, **kwargs) while being wrapped in the new logic.

Basic Example:

def decorators(func):
    def wrapper():
        print("This is about to execute a function...")
        func()
        print("Finished Executing Function!!")
    return wrapper

def say_hello():
    print("Hello User!")

f = decorators(say_hello)
f()

'''
f will look something like this
def f():
    print("This is about to execute a function...")
    print("Hello User!")
    print("Finished Executing Function!!")
'''

# Better Syntax:
@decorators
def say_hello():
    print("Hello User!")

say_hello()

Another Useful Example

import time

def timer(func):
    """A decorator that measures a function's execution time."""
    def wrapper(*args, **kwargs):
        start = time.time()
        result = func(*args, **kwargs)
        end = time.time()
        print(f"Time taken: {end - start:.4f}s")
        return result
    return wrapper

@timer
def slow_function():
    time.sleep(2)
    print("Done!")

slow_function()
# Output:
# Done!
# Time taken: 2.0002s