Python argparse:强制列表项唯一 [英] Python argparse: Force a list item to be unique

问题描述

能够使用下面的choices=servers验证列表项很不错.

Being able to validate the list items using choices=servers below is nice.

servers = [ "ApaServer", "BananServer", "GulServer", "SolServer", "RymdServer", "SkeppServer", "HavsServer", "SovServer" ]
parser = argparse.ArgumentParser()
parser.add_argument('-o', '--only', nargs='*', choices=servers, help='Space separated list of case sensitive server names to process')

是否可以强制列表中的项目是唯一的，从而不允许重复?

Is it possible to force an item in the list to be unique, so that no duplicates are allowed?

推荐答案

使用argparse正确丢弃重复项的方法是创建自己的argparse.Action类，该类负责使用其他答案所建议的使用set的方法. :

The way to properly discard duplicates using argparse would be to create your own argparse.Action class that takes care of using set as suggestted by other answers:

import argparse

class UniqueAppendAction(argparse.Action):
    def __call__(self, parser, namespace, values, option_string=None):
        unique_values = set(values)
        setattr(namespace, self.dest, unique_values)

servers = ["ApaServer", "BananServer", "GulServer", "SolServer",
           "RymdServer", "SkeppServer", "HavsServer", "SovServer" ]
parser = argparse.ArgumentParser()
parser.add_argument('-o', '--only', nargs='*', choices=servers, action=UniqueAppendAction,
                    help='Space separated list of case sensitive server names to process')
print parser.parse_args()

示例输出:

$ python test.py -o ApaServer ApaServer
Namespace(only=set(['ApaServer']))

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