python– 浮点随机(？！)精确怪癖

参见英文答案 > Is floating point math broken?                                    28个
>            Why do simple math operations on floating point return unexpected (inaccurate) results in VB.Net and Python?                                    4个
我刚开始学习python,我偶然发现了一个特殊性

python版本：

Python 2.7.2 (default,Jul 20 2011,02:32:18) [GCC 4.2.1 (LLVM,
Emscripten 1.5,Empythoned)] on linux2

上：http://repl.it/languages/Python

使用解释器分配：

    pi = 3.141 // 3 places decimal precision    #tyPing pi  & pressing return puts 3.141   type(pi)=> 

好的浮点精度因为不精确而臭名昭着;
但为什么只有4点精度得到那个“尾巴”呢？

也：

 pi2 = 3.1415100000000002 pi == pi2 # pi was assigned 3.1415 => True print(pi2) 3.14151 # Where's my precision? 

variance = .0001floatsEqual = lambda f1,f2: f1 - variance <= f2 and f1 + variance >= f2if (floatsEqual(3.1415,3.1415 + 1 - 1)):    pass