argparse nargs="+"正在吃位置参数 [英] Argparse nargs="+" is eating positional argument

问题描述

这是我的解析器配置的一个小节

Here's a subsection of my parser configuration

parser.add_argument(
    'infile', help="The file to be imported",
    type=argparse.FileType('r'), default=sys.stdin
)

parser.add_argument(
    '--carpark', nargs='+', dest='CarparkID', type=int, default=[],
    help="One or many carpark IDs"
)

然而，--carpark 参数似乎过于贪婪，并且会吃掉它后面的任何东西:

However, the --carpark argument seems to be too greedy and eats anything that follows it:

$ mycommand --carpark 17 ~/path-to-file
mycommand: error: argument --carpark: invalid int value: '/home/oli/path-to-file'

有什么好的方法可以解决这样的问题?我需要将整数 ID 列表传递到命令中，但还有一个位置文件(也可以是标准输入).

What's a good way around something like this? I need to pass a list of integer IDs into the command but also have a positional file (which can also be stdin).

是否有——例如——一个非贪婪的 nargs 选项，它只会解析尽可能多的有意义的内容?

Is there —for example— a non-greedy nargs option that will only parse as much of this as makes sense?

推荐答案

如果您想指定多个停车场 ID，我会执行以下两种操作之一，而不是使用 nargs='+':

If you want to specify multiple car park IDs, I would do one of two things instead of using nargs='+':

1. 每个 ID 使用一次该选项 (mycommand --carpark 17 --carpark 18)

parser.add_argument('--carpark',
                    dest='carpark_ids',
                    type=int,
                    action='append',
                    default=[],
                    help="One carpark ID (can be used multiple times)"
)

改为使用单个逗号分隔的参数 (mycommand --carpark 17,18)

def intlist(s):
    rv = []
    for x in s.split(','):
        try:
            x = int(x)
        except ValueError:
            raise ArgumentTypeError("Non-integer carpark id {x}" % (x,))
        rv.append(x)
    return rv

parser.add_argument('--carpark',
                    type=intlist,
                    dest='carpark_ids',
                    default=[],
                    help="One or more carpark IDs"
)

稍加工作，您可以修改它以允许多次使用 --carpark 将其所有值累积到一个列表中.

With a little more work, you could modify this to allow multiple uses of --carpark to accumulate all its values into a single list.

我不是特别喜欢的第三种选择是放弃位置参数，而是将其作为可选参数.(mycommand --carpark 17 18 --infile ~/path-to-file).

A third alternative, one I'm not particularly fond of, is to abandon the positional argument, making it an optional argument instead. (mycommand --carpark 17 18 --infile ~/path-to-file).

parser.add_argument('--infile',
                    help="The file to be imported",
                    type=argparse.FileType('r'),
                    default=sys.stdin
)

parser.add_argument('--carpark',
                    nargs='+',
                    dest='CarparkID',
                    type=int,
                    default=[],
                    help="One or many carpark IDs"
)

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