Python argparse和控制/覆盖退出状态代码

问题描述

除了修补argparse源之外，还有什么方法可以控制退出状态代码，当调用parse_args()时是否应该有问题，例如缺少必需的开关?

Apart from tinkering with the argparse source, is there any way to control the exit status code should there be a problem when parse_args() is called, for example, a missing required switch?

推荐答案

我不知道有任何机制可以根据参数指定退出代码.您可以捕获在.parse_args()上引发的SystemExit异常，但是我不确定接下来如何确定是什么 引起了错误.

I'm not aware of any mechanism to specify an exit code on a per-argument basis. You can catch the SystemExit exception raised on .parse_args() but I'm not sure how you would then ascertain what specifically caused the error.

编辑:对于任何寻求实用解决方案的人，情况如下:

For anyone coming to this looking for a practical solution, the following is the situation:

arg解析失败时，会适当引发
• ArgumentError().它传递了参数实例和一条消息
• ArgumentError()不会不将参数存储为实例属性，尽管会被传递(这很方便)
• 可以通过子类化ArgumentParser，重写.error()并从sys.exc_info()获取异常来重新引发ArgumentError异常

• ArgumentError() is raised appropriately when arg parsing fails. It is passed the argument instance and a message
• ArgumentError() does not store the argument as an instance attribute, despite being passed (which would be convenient)
• It is possible to re-raise the ArgumentError exception by subclassing ArgumentParser, overriding .error() and getting hold of the exception from sys.exc_info()

这意味着下面的代码(虽然很丑陋)使我们能够捕获ArgumentError异常，掌握有问题的参数和错误消息，并按我们认为合适的方式进行操作:

All that means the following code - whilst ugly - allows us to catch the ArgumentError exception, get hold of the offending argument and error message, and do as we see fit:

import argparse
import sys

class ArgumentParser(argparse.ArgumentParser):    
    def _get_action_from_name(self, name):
        """Given a name, get the Action instance registered with this parser.
        If only it were made available in the ArgumentError object. It is 
        passed as it's first arg...
        """
        container = self._actions
        if name is None:
            return None
        for action in container:
            if '/'.join(action.option_strings) == name:
                return action
            elif action.metavar == name:
                return action
            elif action.dest == name:
                return action

    def error(self, message):
        exc = sys.exc_info()[1]
        if exc:
            exc.argument = self._get_action_from_name(exc.argument_name)
            raise exc
        super(ArgumentParser, self).error(message)

## usage:
parser = ArgumentParser()
parser.add_argument('--foo', type=int)
try:
    parser.parse_args(['--foo=d'])
except argparse.ArgumentError, exc:
    print exc.message, '\n', exc.argument

未经任何有用的方式测试.通常，如果违反赔偿，不要怪我.

Not tested in any useful way. The usual don't-blame-me-if-it-breaks indemnity applies.

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