Python Argparse - 基于另一个参数的值有条件地需要参数 [英] Python Argparse - conditionally required arguments based on the value of another argument

问题描述

我正在尝试编写一个守护程序服务，该服务可以在命令行中进行控制.比如启动服务

I am trying to write a daemon service, which can be controlled in the command line. For example, to start the service

python3 test.py -c start -d/mydownloadfolder/-j/myconfig.json

停止服务，

python3 test.py -c stop

-d -j 参数仅在我启动服务时才需要.因此，我需要根据另一个参数的值来实现有条件要求的参数.

The -d -j parameters are required only when I start the service. Therefore, I need to implement conditionally required arguments based on the value of another argument.

我进行了一些搜索，发现了这篇有用的帖子 Python Argparse 有条件地要求的参数不同之处在于:我需要检查--command"的值而不是检查--command"的存在.

I did some search and found this useful post Python Argparse conditionally required arguments The difference is: instead of checking the existence of '--command', I need to check the value of the '--command'.

这是我的初步解决方案:

Here is my tentative solution:

PARSER.add_argument('-c', '--command', required=True, help='provide a valid command: start, stop, restart, or status')
NEED_MORE_ARGS = PARSER.parse_args().command.lower().startswith('start')
PARSER.add_argument('-d', '--download', required=NEED_MORE_ARGS , default=LOCAL_DOWNLOAD, help='set account download folder')
PARSER.add_argument('-j', '--input',  required=NEED_MORE_ARGS, default=JSON_INPUT, help='set input json file')

我解析了中间的args得到NEED_MORE_ARGS(boolean)，然后添加其他args.代码似乎不干净.有没有更好的方法来做到这一点?

I parsed the args in the middle to get NEED_MORE_ARGS(boolean), and then add other args. The code seems not clean. Is there a better way to do this?

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更新:暂定解决方案不起作用.:(

Updated: The tentative solution does not work. :(

推荐答案

我认为你可以使用两个解析器来做到这一点:

I think you can use two parsers to do that:

import argparse

if __name__ == '__main__':
    command_parser = argparse.ArgumentParser()
    command_parser.add_argument('-c', '--command', required=True,
                                help='provide a valid command: start, stop, restart, or status')

    if command_parser.parse_known_args()[0].command.lower().startswith('start'):
        option_parser = argparse.ArgumentParser()
        option_parser.add_argument('-d', '--download', required=True, help='set account download folder')
        option_parser.add_argument('-j', '--input', required=True, help='set input json file')
        option_parser.parse_known_args()

或者您可以使用子解析器，这在您的情况下可能更好:

or you can use a subparser, which is probably better in your case:

import argparse

if __name__ == '__main__':
    command_parser = argparse.ArgumentParser()

    subparsers = command_parser.add_subparsers(help='Choose a command')

    start_parser = subparsers.add_parser('start', help='"start" help')
    start_parser.add_argument('-d', '--download', required=True, help='set account download folder')
    start_parser.add_argument('-j', '--input', required=True, help='set input json file')
    start_parser.set_defaults(action=lambda: 'start')

    stop_parser = subparsers.add_parser('stop', help='"stop" help')
    stop_parser.set_defaults(action=lambda: 'stop')

    command_parser.parse_args()

在这种情况下，命令行语法会有所不同:

in this case command line syntax will be bit different:

python3 test.py start -d /mydownloadfolder/ -j /myconfig.json

python3 test.py stop

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