问题描述
我正在使用arange函数来定义for循环迭代并获得意外结果.
I am using the arange function to define my for loop iterations and getting unexpected results.
i = arange(7.8,8.4,0.05)
print i
满足以下条件:
[ 7.8 7.85 7.9 7.95 8. 8.05 8.1 8.15 8.2 8.25 8.3 8.35 8.4 ]
但是使用的终止值为8.35如下
yet using the stop value of 8.35 as follows
i = arange(7.8,8.35,0.05)
产生以下结果
[ 7.8 7.85 7.9 7.95 8. 8.05 8.1 8.15 8.2 8.25 8.3 ]
但是我希望我的射程结束于8.35！我知道我可以使用大于8.35且小于< 8.4达到我的结果，但是为什么会有所不同并且在我看来却不一致?
But I want my range to end at 8.35! I know I can use the stop value of > 8.35 and < 8.4 to achieve my result, but why is it different and in my mind, inconsistent?
我正在使用2.7版
推荐答案
也许与浮点数的限制有关.由于机器的精度，不可能将所有可能的值完美地存储为浮点数.例如:
Perhaps it has to do with limitations on floating point numbers. Due to machine precision, it is not possible to store every conceivable value perfectly as a floating point. For example:
>>> 8.4
8.4000000000000004
>>> 8.35
8.3499999999999996
因此，作为浮点数的8.4略大于8.4的实际值，而作为浮点数的8.35则稍小一点.
So, 8.4 as a floating point is slightly greater than the actual value of 8.4, while 8.35 as a floating point is a tiny bit less.
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