Argparse快捷方式选项，用于组合其他选项 [英] Argparse shortcut option for combining other options

问题描述

假设我有一个输入文件选项和一个输出文件选项.如何创建将两者结合的选项?例如:

  $ ./my_script.py -i input.txt -o output.txt 

可以组合为:

  $ ./my_script.py --io input_output.txt 

您可能会说我可以做 -io 来组合两个选项，但是 -io filename 是 -i -o filename 的快捷方式>，而不是 -i filename -o filename .

我认为可以在我的 .add_argument()调用中添加 dest =('input'，'output') dest 必须是字符串.

我尝试添加一个互斥的组，一侧为-io ，另一侧为一组 -i 和 -o 但是，当使用-help 运行程序时， -i 和 -o 的帮助文本不再显示./p>

 用法:myscript.py [-h] [--io] [-i INPUT] [-o OUTPUT]可选参数:-h，--help显示此帮助消息并退出--io使用文件作为输入和输出 

此外，互斥的部分似乎也不起作用.我仍然可以使用-io 以及单独的 -i 和 -o 选项调用脚本，并且不会出现错误./p>

这是我的基本代码:

  import argparse解析器= argparse.ArgumentParser()parser.add_argument(-i"，"--input"，help =输入文件")parser.add_argument(-o"，"--output"，help =输出文件")parser.parse_args() 

带有组的代码:

  import argparse解析器= argparse.ArgumentParser()Exclusive = parser.add_mutually_exclusive_group()Exclusive.add_argument(-io"，help =输入和输出")子= Exclusive.add_argument_group()sub.add_argument(-i"，"--input"，help =输入文件")sub.add_argument(-o"，"--output"，help =输出文件")args = parser.parse_args()如果是args.io:in_file = out_file = args.io别的:in_file = args.inputout_file = args.output 

解决方案

比起提出解决方案，更容易解释为什么事情不起作用.

是，目的地必须是字符串；没有提供 dest 值的列表或元组.但是您的 in_file = out_file = args.io 地址可以很好地解决这个问题.您还可以使用:

  args.in_file = args.out_file = args.io 

在解析后按摩 args 值没有问题.

argument_group 并不是为嵌套而设计的，也不是将"any"(或"and")逻辑添加到 mutually_exclusive_group 的一种方式.也许在遥远的将来，将会有一种方法来定义一套完整的逻辑组合，但现在还不是.实际上，进行测试并不难.很难定义API和使用格式.

还请记住， mutually_exclusive_group 用于格式化用法并测试参数的共现性，而 argument_group 用于对参数帮助行进行分组.两个非常不同的目的.

如果 -i 是 store_true 自变量，则 -io文件名将被理解为 -i -o文件名.但是也要翻译它 -i filename -o filename 不在当前代码中(并且可能不够常见，不足以提供补丁).

如果您仍然想使用 -i ， -o 和-io (我更喜欢使用-对于2个字符标记)，我可以建议几件事:

• 编写一个自定义用法来演示您想要的内容.如果很难编写清晰的用法，则您的设计可能太复杂了.

解析后，

• 进行自己的独占组测试. args.in_file为None 是测试标记是否已使用的好方法.另一种可能性是定义默认值，这样您就不必在乎用户使用哪种组合.

Let's say I have an input file option and an output file option. How can I create an option that combines the two? For example:

$ ./my_script.py -i input.txt -o output.txt

could be combined as:

$ ./my_script.py --io input_output.txt

You might say that I could do -io to combine both options, but -io filename is a shortcut for -i -o filename, not -i filename -o filename.

I thought that it might be possible to add dest=('input', 'output') to my .add_argument() call, but that raised an error that dest must be a string.

I tried adding a mutually exclusive group with --io on one side and a group of -i and -o on the other side, but the help texts for -i and -o did not show up any more when the program was run with --help:

usage: myscript.py [-h] [--io] [-i INPUT] [-o OUTPUT]

optional arguments:
  -h, --help  show this help message and exit
  --io        Use file as both input and output

Also, the mutually exclusive part didn't seem to work. I am still allowed to call the script with --io and the individual -i and -o options, and no error is raised.

Here is my skeleton code:

import argparse

parser = argparse.ArgumentParser()

parser.add_argument("-i", "--input", help="Input file")
parser.add_argument("-o", "--output", help="Output file")

parser.parse_args()

The code with groups:

import argparse

parser = argparse.ArgumentParser()

exclusive = parser.add_mutually_exclusive_group()
exclusive.add_argument("--io", help="Input and Output")

sub = exclusive.add_argument_group()
sub.add_argument("-i", "--input", help="Input file")
sub.add_argument("-o", "--output", help="Output file")

args = parser.parse_args()

if args.io:
    in_file = out_file = args.io
else:
    in_file = args.input
    out_file = args.output

解决方案

It is easier to explain why things don't work than to suggest a solution.

Yes, dest must be a string; there's no provision for a list or tuple of dest values. But your in_file = out_file = args.io addresses that issue just fine. You could have also used:

 args.in_file=args.out_file = args.io

There's nothing wrong with massaging the args values after parsing.

argument_group is not designed for nesting, nor is it a way of adding 'any' (or 'and') logic to the mutually_exclusive_group. Maybe in the distant future there will be a way of defining a full set of logical combinations, but not now. Actually it isn't hard to do the tests; it's hard to define the API and the usage formatting.

Also keep in mind that mutually_exclusive_group is used to format the usage and test for co_ocurrance of arguments, while argument_group is used to group argument help lines. Two very different purposes.

If -i was a store_true argument then -io filename would be understood as -i -o filename. But translating it too -i filename -o filename is not in the current code (and probably not common enough to warrant a patch).

If you still want to use -i, -o and --io (I prefer -- for 2 character flags) I can suggest a couple of things:

• write a custom usage that demonstrates what you want. If it is hard to write a clear usage, then your design is probably too complicated.

• do your own exclusive groups testing after parsing. args.in_file is None is a good way of testing whether a flag has been used or not. Another possibility is to define defaults such that you don't care which combination the user uses.

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