为什么在某些情况下，Python中的类型转换/乘法会失败？ [英] Why does type-conversion/multiplication fail in Python for certain cases?

问题描述

我当然是Python的新手。因此，我很难理解下面的代码给我的结果i = 15和i = 21.在所有其他情况下，我的期望是。

I'm certainly a newbie to Python. Hence, I'm struggling to understand the results that the following bit of code gives me for i = 15 and i = 21. In all other cases is does what I expect.

import numpy as np

i_values = []
results = []
results2 = []

for i in range(27):
  i_values.append(i)
  result = np.int((i*0.02+0.03)*1.e2)
  results.append(result)

  result2 = (i*0.02+0.03)*1.e2
  results2.append(result2)

print i_values
print results
print results2

我的问题是：为什么代码适用于大多数数字但是某些值失败我？我可以解决这个问题

My question is: Why is the code working for most numbers but fails for certain values of i? I could solve the problem by

result = np.int(np.rint(((i*0.02+0.03)*1.e2))

但我只是想了解为什么它首先发生。

but I just want to understand why it occurs in the first place.

提前谢谢。

推荐答案

我认为这个链接应该给你一个见解：

I think this link should give you an insight:

为什么要浮动点数不准确？

这是可以理解的，因为如果比较不同语言处理它们之间的结果，结果可能会略有不同。在python中使用之间的简单例子只是谷歌搜索答案：

It is understandable since the results can be slightly different due to precision if compared between how different languages deal with them. A quick example between using in python and just googling the answer:

Python示例

Google示例

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