Python数学是错误的

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Possible Duplicate:
Python rounding error with float numbers

Python 2.7.3 (v2.7.3:70274d53c1dd, Apr  9 2012, 20:52:43) 
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "copyright", "credits" or "license()" for more information.
>>> 4.2 - 1.8
2.4000000000000004
>>> 1.20 - 1.18
0.020000000000000018
>>> 5.1 - 4
1.0999999999999996
>>> 5 - 4
1
>>> 5.0 - 4.0
1.0

为什么Python的数学错了？

Answer 1

对于浮点运算如何工作的严格指导，请完成有关如何计算答案中错误大小的说明，您需要：

What Every Computer Scientist Should Know About Floating-Point Arithmetic

一旦你读过，你应该去寻找8087上的注释，特别是，因为它执行IEEE 754很差，这可能会在你的生活中引起新的令人兴奋的问题。

Answer 2

你已经在计算机科学上达到了一个新的水平，而且你已经成年了。

因此，你现在已经为下一步做好了准备。我得到了BDFL本人的授权，向您透露以下超级机密文件。古人明白了，先破译了，现在，你也要破译！

The Floating Point Guide

小心对待这份文件！只跟你认识的人分享这个，他们得出了同样令人困惑的结论！

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