Python 2.6.6中的小数和科学计数法问题 [英] Problems with decimals and scientific notation in Python 2.6.6

问题描述

在某些情况下，我难以使用十进制值进行算术运算，而在其他情况下，则需要将其用作字符串。具体来说，我有一个费率列表，例如：

I'm having difficulty with decimal values that I need to use for arithmetic in some cases and as strings in others. Specifically I have a list of rates, ex:

rates=[0.1,0.000001,0.0000001]

我正在使用它们指定图像的压缩率。我首先需要将这些值作为数字，因为我需要能够对它们进行排序以确保它们处于特定顺序。我还希望能够将这些值中的每一个转换为字符串，因此我可以1）将比率嵌入文件名中，以及2）将比率和其他详细信息记录在CSV文件中。第一个问题是，将小数点后6位以上的任何浮点数转换为字符串时，其格式都是科学的：

And I am using these to specify the compression rates for images. I need to initially have these values as numbers because I need to be able to sort them to make sure they are in a specific order. I also want to be able to convert each of these values to strings so I can 1) embed the rate into the filename and 2) log the rates and other details in a CSV file. The first problem is that any float with more than 6 decimal places is in scientific format when converted to a string:

>>> str(0.0000001)
'1e-07'

所以我尝试使用Python的Decimal模块但它还将一些浮点数转换为科学计数法（似乎与我阅读的文档相反）。例如：

So I tried using Python's Decimal module but it is also converting some floats to scientific notation (seemingly contrary to the docs I've read). Ex:

>>> Decimal('1.0000001')
Decimal('1.0000001')
# So far so good, it doesn't convert to scientific notation with 7 decimal places
>>> Decimal('0.0000001')
Decimal('1E-7')
# Scientific notation, back where I started.

我也按照多篇文章中的建议研究字符串格式，但是我没有任何内容运气。这个Python新手会赞赏任何建议和指针。

I've also looking into string formatting as suggested in multiple posts, but I've not had any luck. Any suggestions and pointers are appreciated by this Python neophyte.

推荐答案

您必须指定字符串格式，然后：

You have to specify the string format then:

["%.8f" % (x) for x in rates]

这将产生 ['0.10000000'，'0.00000100'，'0.00000010'] 。也可以使用十进制。

This yields ['0.10000000', '0.00000100', '0.00000010']. Works with Decimal, too.

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