本文介绍了Python3舍入到最接近的偶数的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
Python3.4会四舍五入到最接近的偶数(在平局的情况下).
Python3.4 rounds to the nearest even (in the tie-breaker case).
>>> round(1.5)
2
>>> round(2.5)
2
但是似乎只有四舍五入为整数时才这样做.
But it only seems to do this when rounding to an integer.
>>> round(2.75, 1)
2.8
>>> round(2.85, 1)
2.9
在上面的最后一个示例中，当四舍五入到最接近的偶数时，我希望答案是2.8.
In the final example above, I would have expected 2.8 as the answer when rounding to the nearest even.
为什么两种行为之间存在差异?
Why is there a discrepancy between the two behaviors?
推荐答案
浮点数仅是近似值； 2.85不能精确地表示为 :
Floating point numbers are only approximations; 2.85 cannot be represented exactly:
>>> format(2.85, '.53f')
'2.85000000000000008881784197001252323389053344726562500'
它略高于 2.85.
0.5和0.75 可以用二进制分数精确表示(分别为1/2和1/2 + 1/4).
0.5 and 0.75 can be represented exactly with binary fractions (1/2 and 1/2 + 1/4, respectively).
round()函数对此进行了明确记录:
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