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Python decorator pattern

Decorators are everywhere in Python - Flask routes, logging, caching. AI generates them constantly.

pythondecoratorshigher-order functionswrapping
python
import time

def timer(func):
    def wrapper(*args, **kwargs):
        start = time.time()
        result = func(*args, **kwargs)
        end = time.time()
        print(f"{func.__name__} took {end - start:.2f}s")
        return result
    return wrapper

@timer
def slow_sum(numbers):
    time.sleep(0.1)
    return sum(numbers)

output = slow_sum([1, 2, 3, 4, 5])

Question

What does @timer do, and what is the value of output?

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