问题描述
我写了下面的code用于生成与花车范围：
I have written the following code for generating a range with floats:
def drange(start, stop, step):
result = []
value = start
while value <= stop:
result.append(value)
value += step
return result
当调用本声明此功能：
print drange(0.1,1.0,0.1)
我希望获得此：
[0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0]
不过，我得到以下，而不是：
But I obtain the following, instead:
[0.1, 0.2, 0.30000000000000004, 0.4, 0.5, 0.6, 0.7, 0.7999999999999999, 0.8999999999999999, 0.9999999999999999]
这是为什么？我该如何解决？
Why is this?, and how can I fix it?
谢谢！
推荐答案
这是如何浮点数的工作。不能重新present实数的无限数目在一个有限数目的位，所以有一些截短。你应该看一看 ：
That's how floating-point numbers work. You can't represent an infinite number of real numbers in a finite number of bits, so there is some truncation. You should take a look at What Every Programmer Should Know About Floating-Point Arithmetic:
为什么不是我的号码，像0.1 + 0.2加起来一个漂亮的圆0.3，而是我得到一个怪异的结果像0.30000000000000004？
由于内部，电脑使用的格式（二进制浮点）不能准确地重新present一个像0.1，0.2或0.3的。
Because internally, computers use a format (binary floating-point) that cannot accurately represent a number like 0.1, 0.2 or 0.3 at all.
当code编译或间preTED，你的0.1已经四舍五入到该格式的最接近的数字，甚至计算发生之前导致小的舍入误差。
When the code is compiled or interpreted, your "0.1" is already rounded to the nearest number in that format, which results in a small rounding error even before the calculation happens.
使用圆（周数，k）小数点后四舍五入给定的浮点值 K 数字（所以你的情况下，使用轮（数字，1）为一个数字）。
Use round(number, k) to round a given floating-point value to k digits after the decimal (so in your case, use round(number, 1) for one digit).
这篇关于为什么Python的节目`0.2 + 0.1`为'0.30000000000000004`？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！