python - Python的reduce()会短路吗？

Question

如果我这样做:

result = reduce(operator.and_, [False] * 1000)

它会在第一个结果后停止吗？ (因为 False & anything == False)

类似地:

result = reduce(operator.or_, [True] * 1000)

Answer 1

事实并非如此。在这种情况下，您的替代方案是 any和 all .

result = reduce(operator.and_, [False] * 1000)
result = reduce(operator.or_, [True] * 1000)

可以替换为

result = all([False] * 1000)
result = any([True] * 1000)

短路。

计时结果显示差异:

In [1]: import operator

In [2]: timeit result = reduce(operator.and_, [False] * 1000)
10000 loops, best of 3: 113 us per loop

In [3]: timeit result = all([False] * 1000)
100000 loops, best of 3: 5.59 us per loop

In [4]: timeit result = reduce(operator.or_, [True] * 1000)
10000 loops, best of 3: 113 us per loop

In [5]: timeit result = any([True] * 1000)
100000 loops, best of 3: 5.49 us per loop