numpy.isnan(value) 与 value == numpy.nan 不一样? [英] numpy.isnan(value) not the same as value == numpy.nan?

问题描述

为什么我得到以下信息:

<预><代码>>>>v南>>>类型(v)<输入'numpy.float64'>>>>v == np.nan错误的>>>np.isnan(v)真的

我会认为两者应该是等价的?

解决方案

nan != nan.这就是 nan 上的相等比较是如何定义的.决定这个结果对于数值算法比替代方法更方便.这就是 isnan 存在的具体原因.

Why am I getting the following:

>>> v
nan
>>> type(v)
<type 'numpy.float64'>
>>> v == np.nan
False
>>> np.isnan(v)
True

I would have thought the two should be equivalent?

解决方案

nan != nan. That's just how equality comparisons on nan are defined. It was decided that this result is more convenient for numerical algorithms than the alternative. This is specifically why isnan exists.

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