Python打开文本文件的方法，选择每个第n个值，然后保存到文本文件.

问题描述：

我有一个包含 57,600,000 百万行值的文本文件.这些值位于文本文件的单列中.它们代表一个重复 2400 次的 150(列)x 160(行)矩阵.我希望完成 2 个不同的操作，每个操作有 3 个目标.

I have a text file that contains 57,600,000 million lines of values. These values are in a single column in the text file. They represent a 150(column) x 160(row) matrix repeated 2400 times. I wish to complete 2 different operations, each with 3 objectives.

操作 1(列)

打开文本文件
选择每第 n 个数据点
将所选值保存到另一个文本或 .csv 文件

操作 2(行)

打开文本文件
从每第 n 行开始选择一个值范围 (150)
将所选值保存到另一个文本或 .csv 文件

这样做的目的是先打印一个矩阵列，然后再打印一行.我是 python 新手用户，正在使用 spyder 运行其他脚本.如果您愿意为我编写脚本，请描述我需要替换的内容以获得所需的结果.我已经浏览了其他类似的帖子，但找不到一个足够相似的帖子，我可以根据自己的需要进行编辑，以我有限的知识.

The point of this is to print a matrix column and then a row. I am a novice python user and am using spyder to run other scripts. If you would be kind enough to write a script for me, please be descriptive on what I would need to replace to get the desired results. I have looked through other similar postings but cannot find a thread that is similar enough that I could edit to my needs, with my limited knowledge.

非常感谢您的关注以及您能提供的任何帮助.

Thank you very much for looking and any assistance you can give.

答

Python 中的文件是迭代器，这意味着它们可以循环使用，或者对其应用迭代操作.

Files in Python are iterators, meaning they can be looped over, or have iteration operations applied to them.

例如，要获取每 5 行，将是:

To get every 5th line, for example, would be:

import itertools

with open(filename, 'r') as f:
    fifthlines = itertools.islice(f, 0, None, 5)
    for line in fifthlines:
        # do something with line

您也可以使用 islice() 来跳过行；这里我们跳过 10 行，然后读取 10 行:

You can use islice() to skip lines too; here we skip 10 lines, then read 10:

for line in itertools.islice(f, 10, 20):
    # do something with this 10th line

你可以吞下一个系列；因为跳过，然后读取 0 行会引发 StopIteration 信号，我们通过使用 next() 并传入要返回的默认值来吞下它:

You can swallow a series; because skipping, then reading 0 lines raises a StopIteration signal, we swallow that by using next() and passing in a default value to be returned instead:

next(itertools.islice(f, 42, 42), None)  # skip 42 lines, don't read more

使用 itertools 库，以及快速浏览 Python 教程，您可以很容易地找出脚本的其余部分.

With the itertools library, and a quick scan through the Python tutorial you can figure out the rest of the script easily enough.

Python打开文本文件的方法，选择每个第n个值，然后保存到文本文件.

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