Python浮点数字表示 [英] Python float numbers representation

问题描述

可能重复：

浮点限制

您好，

也许这个答案很简单。我正在玩Python解释器。

 >>> 1 
 1 
>>> 1.1 
 1.1000000000000001 
>>> 1.2 
 1.2 
  

为什么 1.1 被解释为 1.1000000000000001 ？

解决方案

From 浮点指南：

为什么我的数字，比如0.1 + 0.2加起来好一轮0.3，而
反而得到一个奇怪的结果，比如
0.30000000000000004？

由于内部计算机使用
格式（二进制浮点），所以
不能准确地表示一个数字
，如0.1,0.2或0.3 。

在编译代码或解释
时，您的0.1已经被
四舍五入到
格式的最接近的数字，即使在
计算发生之前，这也会导致一个很小的
舍入误差。

Possible Duplicate:
Floating Point Limitations

Hi there,

maybe this has a very simple answer. I was playing around with the Python interpreter.

>>> 1
1
>>> 1.1
1.1000000000000001
>>> 1.2
1.2

Why 1.1 was interpreted as 1.1000000000000001?

解决方案

From The Floating-Point Guide:

Why don’t my numbers, like 0.1 + 0.2 add up to a nice round 0.3, and instead I get a weird result like 0.30000000000000004?

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.

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.

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