🎀 Lesson 63: Python Decorators (Functions Enhancing Functions)
1. What Is a Decorator?
In short → A decorator is a kind of higher-order function that takes a function as input, adds extra features to it, and returns the enhanced version.
In detail → A decorator is a higher-order function that takes another function as input, adds extra functionality, and returns a new function.
2. Why Use Decorators?
- You can add extra features to a function without changing it
- They help you reuse code
- Commonly used for logging, authentication, and performance measurement
3. Summary
✅ Decorator = a higher-order function that enhances a function
✅ Syntax → @decorator_name
✅ Use cases → logging, authentication, performance, caching
✅ Built-in decorators → @staticmethod, @classmethod, @property
python
# ===== 1. Basic Decorator =====
def my_decorator(func):
def wrapper():
print("Before function runs")
func()
print("After function runs")
return wrapper
@my_decorator
def say_hello():
print("Hello!")
print("===== Basic Decorator =====")
say_hello()
# ===== 2. Decorator with Arguments =====
print(f"\n===== Decorator with Arguments =====")
def my_decorator(func):
def wrapper(*args, **kwargs):
print("Function is running...")
return func(*args, **kwargs)
return wrapper
@my_decorator
def add(a, b):
return a + b
print(f"add(5, 3) = {add(5, 3)}")
# ===== 3. Logging Decorator =====
print(f"\n===== Logging Decorator =====")
def log(func):
def wrapper(*args, **kwargs):
print(f"Calling {func.__name__}")
result = func(*args, **kwargs)
print(f"{func.__name__} finished")
return result
return wrapper
@log
def greet(name):
print(f"Hello, {name}")
greet("Sai")
# ===== 4. Timing Decorator =====
print(f"\n===== Timing Decorator =====")
import time
def timing(func):
def wrapper(*args, **kwargs):
start = time.time()
result = func(*args, **kwargs)
end = time.time()
print(f"{func.__name__} took {end - start:.4f} seconds")
return result
return wrapper
@timing
def slow_function():
time.sleep(0.1)
return "Done"
slow_function()
# ===== 5. Built-in Decorators =====
print(f"\n===== Built-in Decorators =====")
print("@staticmethod → Static method in class")
print("@classmethod → Class method")
print("@property → Getter method as property")You should see
===== Basic Decorator ===== Before function runs Hello! After function runs ===== Decorator with Arguments ===== Function is running... add(5, 3) = 8 ===== Logging Decorator ===== Calling greet Hello, Sai greet finished ===== Timing Decorator ===== slow_function took 0.1002 seconds Done ===== Built-in Decorators ===== @staticmethod → Static method in class @classmethod → Class method @property → Getter method as property