Complete Guide to Python Decorators – Enhancing Function Behavior with Reusable Logic

Introduction

Decorators in Python are one of the most elegant features for managing and enhancing the behavior of functions and classes. They allow you to wrap additional logic around existing code without modifying its internal structure. This makes your code cleaner, more modular, and easier to maintain.

Basic Structure of a Decorator

A decorator is a function that takes another function as input and returns a modified version of it:

def my_decorator(func):
    def wrapper():
        print("Before function runs")
        func()
        print("After function runs")
    return wrapper

Using the @ Symbol

To apply a decorator to a function, use the @ symbol:

@my_decorator
def say_hello():
    print("Hello!")

say_hello()

Output:

Before function runs
Hello!
After function runs

Decorators with Arguments

To support functions with arguments, use *args and **kwargs:

def log_decorator(func):
    def wrapper(*args, **kwargs):
        print(f"Calling {func.__name__} with {args} and {kwargs}")
        return func(*args, **kwargs)
    return wrapper

Common Use Cases

• Logging: Track function calls and parameters


• Authentication: Check user access before executing a function


• Caching: Store results to avoid repeated computation


• Timing: Measure execution time of functions

Built-in Python Decorators

Python provides several built-in decorators:

• @staticmethod for defining static methods


• @classmethod for methods that access the class itself


• @property to turn a method into a readable attribute

Nested Decorators

You can apply multiple decorators to a single function:

@auth_check
@log_decorator
def process_data():
    pass

In this case, log_decorator runs first, followed by auth_check.

Conclusion

Decorators in Python are a powerful way to enhance and control function behavior. They help you implement shared logic in a clean, reusable manner. Mastering decorators is a key step toward writing professional, scalable Python code.