Python中舍入浮点数的问题 [英] Problems with Rounding Floats in Python

问题描述

np.round出现问题，np.around不能正确舍入.我不能包含代码，因为当我手动设置值(相对于使用我的数据)时，返回有效，但这是输出:

I'm having a problem with np.round, np.around where it is not rounding properly. I can't include code, because when I do it manually set the value (as opposed to use the my data), the return works, but here is the output:

In [177]: a
Out[177]: 0.0099999998

In [178]: np.round(a,2)
Out[178]: 0.0099999998


In [179]: np.round(a,1)
Out[179]: 0.0

我想念什么? a的dtype是float32，我需要更改吗?

What am I missing? The dtype of a is float32, do I need to change this?

推荐答案

尝试创建np.float32(0.01)，您将看到答案.您将获得已经可以达到的精度.

Try creating np.float32(0.01) and you will see your answer. You are getting the precision you can already.

>>> import numpy as np
>>> x = 0.01
>>> epsilon = 0.01 - np.float32(0.01)
>>> for n in np.arange(x - 10*epsilon, x + 10*epsilon, epsilon):
...     print(repr(np.float32(n)))
...     
0.0099999979
0.0099999979
0.0099999979
0.0099999988
0.0099999988
0.0099999988
0.0099999988
0.0099999998
0.0099999998
0.0099999998
0.0099999998
0.0099999998
0.010000001
0.010000001
0.010000001
0.010000001
0.010000002
0.010000002
0.010000002
0.010000002

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