argparse:将参数与另一个参数相关联

问题描述：

使用argparse，可以重复一个参数并将所有值收集到一个列表中:

With argparse, it's possible to repeat an argument and collect all the values into a list:

parser = ArgumentParser()
parser.add_argument('-o', '--output', action='append')

args = parser.parse_args(['-o', 'output1', '-o', 'output2'])
print(vars(args))
# {'output': ['output1', 'output2']}

我正在寻找一种将标记与这些参数相关联的方法，以便可以执行此操作:

I'm looking for a way to associate flags with each of these arguments, so that it's possible to do this:

args = parser.parse_args(['-o', 'output1', '--format', 'text',
                          '-o', 'output2', '--format', 'csv'])

并获得这样的输出(或类似的结果):

And get an output like this (or something similar):

{'output': {'output1': {'format': 'text'},
            'output2': {'format': 'csv'}
           }
}

理想情况下，这些标志应遵循通常的语义-例如，-format 可以是可选的，或者每个 -o 输出可能有多个参数，在这种情况下，它们应该以任何顺序通过(即 -o output1 -a -b -c 应当等效于 -o output1 -c -a -b ).

Ideally, these flags should follow the usual semantics - for example, --format could be optional, or there could be multiple arguments associated with each -o output, in which case they should be passable in any order (i.e. -o output1 -a -b -c should be equivalent to -o output1 -c -a -b).

这可以用argparse完成吗?

Can this be done with argparse?

答

基于 hpaulj的答案中的代码，我已对实现进行了调整，以使其更加通用.它由2个自定义Action类组成，分别是 ParentAction 和 ChildAction .

Based on the code in hpaulj's answer, I've tweaked the implementation to make it more versatile. It consists of 2 custom Action classes, ParentAction and ChildAction.

parser = argparse.ArgumentParser()
# first, create a parent action:
parent = parser.add_argument('-o', '--output', action=ParentAction)
# child actions require a `parent` argument:
parser.add_argument('-f', '--format', action=ChildAction, parent=parent)
# child actions can be customized like all other Actions. For example,
# we can set a default value or customize its behavior - the `sub_action`
# parameter takes the place of the usual `action` parameter:
parser.add_argument('-l', '--list', action=ChildAction, parent=parent,
                    sub_action='append', default=[])

args = parser.parse_args(['-o', 'output1', '-l1', '-l2',
                          '-o', 'output2', '--format', 'csv',
                          '-o', 'output3', '-f1', '-f2'])
print(args)
# output (formatted):
# Namespace(
#     output=OrderedDict([('output1', Namespace(list=['1', '2'])),
#                         ('output2', Namespace(format='csv', list=[])),
#                         ('output3', Namespace(format='2', list=[]))
#                         ])
# )

注意事项

子级操作必须始终在父级操作之后执行.例如，-format csv -o output1 无效，并显示错误消息.

即使父母不同，也无法注册多个具有相同名称的ChildAction.

Caveats

Child actions must always follow after parent actions. For example, --format csv -o output1 would not work and show an error message.

It's not possible to register multiple ChildActions with the same name, even with different parents.

示例:

parent1 = parser.add_argument('-o', '--output', action=ParentAction)
parser.add_argument('-f', action=ChildAction, parent=parent1)
parent2 = parser.add_argument('-i', '--input', action=ParentAction)
parser.add_argument('-f', action=ChildAction, parent=parent2)

# throws exception:
# argparse.ArgumentError: argument -f: conflicting option string: -f

import argparse

from collections import OrderedDict


class ParentAction(argparse.Action):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, default=OrderedDict(), **kwargs)

        self.children = []

    def __call__(self, parser, namespace, values, option_string=None):
        items = getattr(namespace, self.dest)
        nspace = type(namespace)()
        for child in self.children:
            if child.default is not None:
                setattr(nspace, child.name, child.default)
        items[values] = nspace

class ChildAction(argparse.Action):
    def __init__(self, *args, parent, sub_action='store', **kwargs):
        super().__init__(*args, **kwargs)

        self.dest, self.name = parent.dest, self.dest
        self.action = sub_action
        self._action = None
        self.parent = parent

        parent.children.append(self)

    def get_action(self, parser):
        if self._action is None:
            action_cls = parser._registry_get('action', self.action, self.action)
            self._action = action_cls(self.option_strings, self.name)
        return self._action

    def __call__(self, parser, namespace, values, option_string=None):
        items = getattr(namespace, self.dest)
        try:
            last_item = next(reversed(items.values()))
        except StopIteration:
            raise argparse.ArgumentError(self, "can't be used before {}".format(self.parent.option_strings[0]))
        action = self.get_action(parser)
        action(parser, last_item, values, option_string)

argparse:将参数与另一个参数相关联

注意事项

Caveats

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