Python OOPs

Python SQLite

Examples

Others

Python OOPs

Python SQLite

Examples

Others



Python Decorators


Python decorators are a powerful tool for modifying or extending the behavior of functions or methods without directly modifying their code. They are commonly used for tasks like logging, enforcing access control, memoization, timing, or modifying function arguments.

What are Decorators ?

A decorator is a function that takes another function as an argument and returns a new function (or a modified version of the original). This is achieved using Python's syntactic sugar with the @decorator_name notation.

Syntax 
def decorator_function(original_function):
    def wrapper_function(*args, **kwargs):
        print(f"Wrapper executed before {original_function.__name__}")
        return original_function(*args, **kwargs)
    return wrapper_function

@decorator_function
def display():
    print("Display function ran")

display()

Output

Wrapper executed before display
Display function ran

Examples of Python Decorators

1) Logging

A logging decorator in Python is a tool that adds logging functionality to functions without changing the core logic of the functions. This can make code easier to debug, maintain, and more modular

Syntax 
def logger(func):
    def wrapper(*args, **kwargs):
        print(f"Function {func.__name__} called with {args} {kwargs}")
        return func(*args, **kwargs)
    return wrapper

@logger
def add(a, b):
    return a + b

print(add(3, 5))

Output

Function add called with (3, 5) {}
8

2) Access Control

An access control decorator is a tool that checks if a user has the required permissions before executing a function.

Syntax 
def requires_admin(func):
    def wrapper(user, *args, **kwargs):
        if not user.get("is_admin"):
            raise PermissionError("User is not an admin")
        return func(user, *args, **kwargs)
    return wrapper

@requires_admin
def delete_user(user, user_id):
    print(f"User {user_id} deleted by {user['username']}")

admin_user = {"username": "admin", "is_admin": True}
regular_user = {"username": "guest", "is_admin": False}

delete_user(admin_user, 42)
# delete_user(regular_user, 42)  # Raises PermissionError

Output

User 42 deleted by admin

3) Class Decorators

A Python class decorator adds a class to a function, and it can be achieved without modifying the source code

Syntax 
def uppercase_decorator(func):
    def wrapper(*args, **kwargs):
        result = func(*args, **kwargs)
        return result.upper()
    return wrapper

class Greeter:
    @uppercase_decorator
    def greet(self, name):
        return f"Hello, {name}"

g = Greeter()
print(g.greet("world"))

Output

 HELLO, WORLD