Python Decorators: A Simple Guide

Kien Nguyen kienngd@gmail.com included in category Code

2025-09-08 2025-09-08 263 words 2 minutes

Contents

Python Decorators: A Simple Guide

1 What is a Decorator?

A decorator in Python is a function that modifies the behavior of another function. It adds extra functionality without changing the original function code.

2 Why Use Decorators?

Decorators help you:

Reuse code
Keep functions clean
Add logging, timing, or access control
Make your code more readable

3 Basic Example

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def my_decorator(func):
    def wrapper(*args, **kwargs):
        print("Before function")
        result = func(*args, **kwargs)  # Call original function
        print("After function")
        return result
    return wrapper

@my_decorator
def greet(name):
    print(f"Hello {name}!")

greet("Alice")

Output:

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Before function
Hello Alice!
After function

4 Decorator with Arguments

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def repeat(times):
    def decorator(func):
        def wrapper(*args, **kwargs):
            for _ in range(times):
                result = func(*args, **kwargs)
            return result
        return wrapper
    return decorator

@repeat(times=2)
def say_hello():
    print("Hello!")

say_hello()

Output:

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Hello!
Hello!

5 Real Use Case: Timing Function

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import time

def timer(func):
    def wrapper(*args, **kwargs):
        start = time.time()
        result = func(*args, **kwargs)
        end = time.time()
        print(f"{func.__name__} took {end - start:.2f} seconds")
        return result
    return wrapper

@timer
def slow_function():
    time.sleep(1)
    print("Done!")

slow_function()

Output:

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Done!
slow_function took 1.00 seconds

6 Key Points

Use *args and **kwargs to accept any number of arguments
The decorator wraps the original function
Decorators make code reusable and clean
They are widely used in web frameworks, logging, and testing
(This article was created by Qwen AI)

Contents

Python Decorators: A Simple Guide

Python Decorators: A Simple Guide

1 What is a Decorator?

2 Why Use Decorators?

3 Basic Example

4 Decorator with Arguments

5 Real Use Case: Timing Function

6 Key Points

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