使用python从文件读取浮点数 [英] Reading floats from file with python

问题描述

我的输入文件的格式为:

My input file has the form:

5.0, 1000.0, 100000000000000.0, 115.2712, 230.538, 345.796, 461.0408, 
1.053E-09, 1.839E-09, 1.632E-10, 1.959E-12, 4.109, 3.683, 3.586, 3.650 

每个数字基本上都在一行中.

where every number is essentially in a line.

我想做的是读取所有浮点数，然后仅将第7到10列附加到数组中.

What I want to do is read all the floats, and then append only columns 7 through 10 to an array.

这是我写的:

T=[]
with open("test.txt", "r") as file1:
    for line in file1.readlines():
        f_list = [float(i) for i in line.split(",")]
        T.append(float(f_list[7]))
        T.append(float(f_list[8]))
        T.append(float(f_list[9]))
        T.append(float(f_list[10]))

当我运行上面的代码时，我得到:

When I run the above I get:

ValueError: could not convert string to float:

我认为 float(i)部分出了问题，但我找不到解决方法.

I think there's something wrong with the float(i) part, but I can't find a way around it.

我已经看到人们在这里遇到类似的问题，但是到目前为止，我尝试过的所有修复方法都没有帮助.任何帮助，我们将不胜感激.

I've seen people having similar problems here, but none of the fixes I've tried so far have helped. Any help is greatly appreciated.

推荐答案

没有问题是您的第一行以逗号结尾:

5.0, 1000.0, 100000000000000.0, 115.2712, 230.538, 345.796, 461.0408,
1.053E-09, 1.839E-09, 1.632E-10, 1.959E-12, 4.109, 3.683, 3.586, 3.650 

因此，您要处理仅包含空格的字符串(例如'').并且 float('')失败，因为它不是数字(它实际上报告了这一点):

As a result, you want to process a string that only contains spaces (like ' '). And float(' ') fails since it is not a number (it actually reports this):

>>> float(' ')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: 
>>> float('a')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: 'a'

但是在打印时根本看不到空格.

But a space simply is invisible when printed.

您可以通过在列表理解中添加 filter语句来解决该问题:

You can solve it by adding a filter statement to the list comprehension:

T = []
with open("test.txt", "r") as file1:
    for line in file1.readlines():
        f_list = [float(i) for i in line.split(",") if i.strip()]
        T += f_list[7:11]

此外，由于没有一行具有7-11的浮点数，因此不会起作用.因此，您将永远不会添加这些浮点数.

Furthermore this will not work since none of the lines has 7-11 floats. So you will never add these floats anyway.

但是，您可以使用以下代码:

You can however use the following code:

with open("test.txt", "r") as file1:
    f_list = [float(i) for line in file1 for i in line.split(',') if i.strip()]
    T = f_list[7:11]

这将导致 T 等于:

>>> T
[1.053e-09, 1.839e-09, 1.632e-10, 1.959e-12]

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