是否所有(列表)都使用短路评估? [英] Does all(list) use short circuit evaluation?

问题描述

我希望使用Python all()函数来帮助我计算某些东西，但是如果all()击中False时不立即求值，那么这件事可能会花费更长的时间.我认为这可能是经过短路评估的，但我只是想确定一下.另外，有没有一种方法可以在Python中说明该函数的求值方式?

I wish to use the Python all() function to help me compute something, but this something could take substantially longer if the all() does not evaluate as soon as it hits a False. I'm thinking it probably is short-circuit evaluated, but I just wanted to make sure. Also, is there a way to tell in Python how the function gets evaluated?

推荐答案

是的，它会短路:

>>> def test():
...     yield True
...     print('one')
...     yield False
...     print('two')
...     yield True
...     print('three')
...
>>> all(test())
one
False

从文档:

如果iterable的所有元素都为true(或者iterable为空)，则返回True.等同于:

From the docs:

Return True if all elements of the iterable are true (or if the iterable is empty). Equivalent to:

def all(iterable):
    for element in iterable:
        if not element:
            return False
    return True

---

因此，当return为False时，该函数将立即中断.

---

So when it returns False, then the function immediately breaks.

这篇关于是否所有(列表)都使用短路评估?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！