为什么numpy.power对于小指数返回0，而math.pow返回正确答案? [英] Why does numpy.power return 0 for small exponents while math.pow returns the correct answer?

问题描述

In [25]: np.power(10,-100)
Out[25]: 0

In [26]: math.pow(10,-100)
Out[26]: 1e-100

我希望两个命令都返回1e-100.这也不是一个精度问题，因为即使将精度提高到500后问题仍然存在.是否可以更改某些设置以获得正确答案?

I would expect both the commands to return 1e-100. This is not a precision issue either, since the issue persists even after increasing precision to 500. Is there some setting which I can change to get the correct answer?

推荐答案

哦，比这更糟糕":

In [2]: numpy.power(10,-1)   
Out[2]: 0

但这暗示了正在发生的事情:10是整数，而numpy.power不会将数字强制转换为浮点数.但这有效:

But this is a hint to what's going on: 10 is an integer, and numpy.power doesn't coerce the numbers to floats. But this works:

In [3]: numpy.power(10.,-1)
Out[3]: 0.10000000000000001

In [4]: numpy.power(10.,-100)
Out[4]: 1e-100

但是请注意，幂运算符**，确实会转换为浮点数:

Note, however, that the power operator, **, does convert to float:

In [5]: 10**-1
Out[5]: 0.1

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