收集列表中的所有其他字符串/文件中的行 [英] Gathering every other string from list / line from file

问题描述

我已经编写了大约两个星期的脚本，并且刚刚学会了从文件中读取内容.

I have been scripting for around two weeks, and have just learnt about reading from a file.

我要做的是从原始列表中获取所有其他条目，并将其存储在新列表中.这是最好的方法吗?

What I want to do is get every other entry from my original list and store it in a new list. Is this the best way to do it?

with open("test.txt",mode="r") as myfile:
File = myfile.read().splitlines()

Username = []

for i in range (len(File)):
    if File.index(File[i])%2 == 0 or File.index(File[i]) == 0:
        Username.append(File[i])
print(Username)

请记住，到目前为止，我仅学习Python大约十个小时-我很高兴它甚至可以正常工作.

Please bear in mind that I have only studied Python for around ten hours so far - I'm quite happy that this even seemed to work.

推荐答案

至少有两种方法可以用更少的代码来完成同一件事.

There are at least a couple ways to accomplish the same thing with less code.

Python提供了一种遍历称为切片符号的数组的第n个元素的方法.您可以将整个循环替换为以下行

Python has a way of iterating over every nth element of an array called slice notation. You can replace the entire loop with the following line

Username.extend(File[0::2])

这基本上意味着从索引0开始获取每个2 nd元素，并将其添加到Username数组中.

What this basically means is to grab every 2nd element starting at index 0 and add it to the Username array.

您还可以使用range()函数的其他版本，该函数允许您指定开始，结束和步骤，如此列出.

You can also use a different version of the range() function, that allows you to specify a start, end and step, list so.

for i in range(0, len(File), 2):
    Username.append(File[i])

在此处中记录了range()函数.

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