使用 argparse 时，子解析器本质上是互斥的吗? [英] With argparse are subparsers inherently mutually exclusive?

问题描述

我有一个包含两个主要功能的脚本，升级和配置.我使用子解析器作为指示脚本执行的操作的一种方式，但我想避免将它们一起使用.

I have a script with two primary functions, upgrade and provision. I'm using subparsers as a way to dictate the action being performed by the script but I want to avoid them being used together.

这是代码片段:

import argparse

def main():
    parser = argparse.ArgumentParser()
    subparser = parser.add_subparsers(help='sub-command help')
    parser.add_argument('--user', '-u', help='User', default=None, required=True)
    parser.add_argument('--password', '-p', help='Password', default=None, required=True)
    parser.add_argument('--server', '-s', help='server with Admin functionality', default=None, required=True)
    subparser_prov = subparser.add_parser('provision', help='Provision new managers')
    subparser_prov.set_defaults(which='provision')
    subparser_upgr = subparser.add_parser('upgrade', help='Upgrade worker by replacing them')
    subparser_upgr.set_defaults(which='upgrade')
    subparser_upgr.add_argument('--version', help='Deployment version', default=None)
    args = vars(parser.parse_args())

    print args['user']
    print args['password']

    if args['which'] == 'provision':
        print 'Provisioning new environment!'
    elif args['which'] == 'upgrade':
        print 'Upgrading workers! %s' % args['version']

if __name__ == "__main__":
    main()

我知道解析器和子解析器都支持 add_mutually_exclusive_group() ，但这专门用于参数.使用子解析器有什么方法可以避免它们一起使用吗?

I know that add_mutually_exclusive_group() is supported by both parser and subparser however this is specifically for arguments. With a subparser is there any method for avoiding them being used together?

推荐答案

是的，它们是相互排斥的，尽管机制与 MXGroups 不同.

Yes, they are mutually exclusive, though the mechanism is different from the MXGroups.

subparser = parser.add_subparsers(help='sub-command help')

是一个 add_argument 命令，它创建一个 positional 参数，带有一个特殊的 action 类.除此之外，它还有一个 choices 值.

is an add_argument command that creates a positional argument, with a special action class. Among other things it has a choices value.

subparser.add_parser(...)

创建一个 parser，并将其名称"(和别名)添加到 subparser 的 choices 中.

creates a parser, and adds its 'name' (and aliases) to subparser's choices.

一个位置参数只解析一次，所以只会处理一个子解析器.并且子解析器通常会处理所有剩余的参数.

A positional argument is parsed only once, so only one subparser will be handled. And the subparser usually processes all of the remaining arguments.

有很多问题要解决这个问题——那就是他们想要处理多个子解析器.这样做的方法很棘手，涉及递归(或重复)调用解析器，每次使用较小的原始参数集.

There have been SO questions that ask about getting around that - that is they want to handle multiple subparsers. The way to do that is tricky, and involves calling a parser recursively (or repeatedly), each time with a smaller set of the original arguments.

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