当Python 3中尾随的小数点大于等于0.5时，math.ceil()和round()之间的算法区别是什么? [英] What is the algorithmic difference between math.ceil() and round() when trailing decimal points are >= 0.5 in Python 3?

问题描述

在Python 3中，尾随小数点> = 0.5时math.ceil()和round()之间的算法区别是什么?

What is the algorithmic difference between math.ceil() and round() when trailing decimal points are >= 0.5 in Python 3?

例如，

round(9.5) = 10
round(9.67) = 10
math.ceil(9.5) = 10
math.ceil(9.5) = 10

推荐答案

来自文档，

[...]如果两个倍数相等接近，则向偶数取整 选择(例如，round(0.5)和round(-0.5)均为0，并且 round(1.5)是2).

[...] if two multiples are equally close, rounding is done toward the even choice (so, for example, both round(0.5) and round(-0.5) are 0, and round(1.5) is 2).

但是，math.ceil将始终四舍五入". IE.大于或等于输入的最小整数.

However, math.ceil will always "round" up. I.e. the smallest integer greater than or equal to the input.

此外，当对负数执行时，round和math.ceil有很大差异.

Moreover, round and math.ceil differ greatly when executing on negative numbers.

>>> math.ceil(-2.8)
-2
>>> round(-2.8)
-3

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