L5·Intermediate/Advanced

🎀Decorators

Functions that wrap functions.

decorator@wraps

§ 1Just syntax sugar

@dec above def f is f = dec(f). Decorators are functions taking a callable and returning a callable.

§ 2functools.wraps

Preserves __name__ and __doc__ on the wrapper — always use it.

§ 3Parameterized

A 'decorator factory' returns the actual decorator: @retry(3) → retry(3)(f).

Example

1from functools import wraps
2import time
3
4def timed(fn):
5    @wraps(fn)
6    def wrapper(*a, **k):
7        t = time.perf_counter()
8        r = fn(*a, **k)
9        print(f"{fn.__name__}: {time.perf_counter()-t:.4f}s")
10        return r
11    return wrapper
12
13@timed
14def work():
15    return sum(range(100_000))
16
17work()

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Checkpoint quiz

Question 1 / 2

@decorator above def f is equivalent to:

Iterators & Generators

Comprehensions