Decorators & Generators

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def timer(func):
    import time
    def wrapper(*a, **kw):
        start = time.time()
        result = func(*a, **kw)
        print(f"{func.__name__}: {time.time()-start:.4f}s")
        return result
    return wrapper

@timer
def slow(): import time; time.sleep(1)

def count_up_to(n):
    i = 1
    while i <= n:
        yield i
        i += 1

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# Generator
def countdown(n):
    while n > 0:
        yield n
        n -= 1

for num in countdown(3):
    print("Countdown:", num)

# Generator expression
squares = (x * x for x in range(1, 6))
print("Sum of squares:", sum(squares))

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

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

@logger
def greet(name):
    return f"Hi, {name}!"

print(add(2, 3))
print(greet("Alice"))