Python float - str - 浮动怪异

2022-01-09 00:00:00 python string floating-point floating-accuracy ieee-754

问题描述

>>> float(str(0.65000000000000002))

0.65000000000000002

>>> float(str(0.47000000000000003))

0.46999999999999997     ???

这里发生了什么?如何将 0.47000000000000003 转换为字符串并将结果值转换回浮点数?

What is going on here? How do I convert 0.47000000000000003 to string and the resultant value back to float?

我在 Windows 上使用 Python 2.5.4.

I am using Python 2.5.4 on Windows.

解决方案

str(0.47000000000000003) 给 '0.47' 和 float('0.47') 可以是 0.46999999999999997.这是由于浮点数的表示方式(参见这篇 wikipedia 文章)

str(0.47000000000000003) give '0.47' and float('0.47') can be 0.46999999999999997. This is due to the way floating point number are represented (see this wikipedia article)

注意:float(repr(0.47000000000000003)) 或 eval(repr(0.47000000000000003)) 会给你预期的结果，但你应该使用十进制，如果你需要精确的话.

Note: float(repr(0.47000000000000003)) or eval(repr(0.47000000000000003)) will give you the expected result, but you should use Decimal if you need precision.

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