Decorators

Functions that wrap other functions — the foundation of Flask routing

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Explanation

A is a function that takes another function and extends its behavior without modifying it.

python

def log_calls(func):
    def wrapper(*args, **kwargs):
        print(f"Calling {func.__name__}")
        result = func(*args, **kwargs)
        print(f"Done")
        return result
    return wrapper

@log_calls
def greet(name):
    return f"Hello, {name}!"

greet("Alice")
# Calling greet
# Done

The @decorator syntax is for greet = log_calls(greet).

This is how Flask routes work:

python @app.route("/home") def home(): return "Hello!"

Examples

Timing decorator

Measure how long a function takes

import time

def timer(func):
    def wrapper(*args, **kwargs):
        start = time.time()
        result = func(*args, **kwargs)
        print(f"{func.__name__} took {time.time()-start:.3f}s")
        return result
    return wrapper

@timer
def slow():
    time.sleep(0.1)

slow()  # slow took 0.100s

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