来自sys import argv-“脚本"的功能是什么? [英] from sys import argv - what is the function of "script"

问题描述

我正在阅读艰难地学习Python"，但对第二行的脚本"部分感到困惑.

I am reading "Learn Python the Hard Way" and was confused by the "script" part of the second line.

from sys import argv
script, filename = argv

据我了解，第二行说:script和filename组成argv. 我尝试在没有脚本"部分的情况下运行我的代码，效果很好.我不确定它的目的是什么.

From what I understand, the second line says: script and filename comprise argv. I tried running my code without the "script" part and it worked just fine. I'm not sure what the purpose of it is.

推荐答案

通常，命令行可执行文件的第一个参数是脚本名称，其余参数是预期的参数.

Generally, the first argument to a command-line executable is the script name, and the rest are the expected arguments.

在这里，argv是一个预期包含两个值的列表:脚本名称和参数.使用Python的拆包符号，您可以编写

Here, argv is a list that is expected to contain two values: the script name and an argument. Using Python's unpacking notation, you can write

script = argv[0]
filename = argv[1]

为

script, filename = argv

同时，如果参数数量过多(例如一或三个)，也会引发错误.根据人的代码，这可能是一个好主意，因为它还可以确保没有意外的参数.

while also throwing errors if there are an unexpected number of arguments (like one or three). This can be a good idea, depending on one's code, because it also ensures that there are no unexpected arguments.

但是，以下代码不会导致filename实际上包含文件名:

However, the following code will not result in filename actually containing the filename:

filename = argv

这是因为filename现在是参数列表.为了说明:

This is because filename is now the argument list. To illustrate:

script, filename = argv
print("Script:", script)  # Prints script name
print("Filename:", filename)  # Prints the first argument

filename = argv
print("Filname:", filename)  # Prints something like ["my-script.py", "my-file.txt"]

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