带有nargs>的Python argparse类型和选择限制1个 [英] Python argparse type and choice restrictions with nargs > 1

问题描述

标题几乎说明了一切.如果我的nargs大于1，是否有任何方法可以对已解析的单个args设置限制(例如，选择/类型)?

The title pretty much says it all. If I have nargs greater than 1, is there any way I can set restrictions (such as choice/type) on the individual args parsed?

这是一些示例代码:

parser = argparse.ArgumentParser()
parser.add_argument('-c', '--credits', nargs=2,
    help='number of credits required for a subject')

对于-c参数，我需要指定一个主题以及需要多少学分.该科目应限于预定义的科目列表，所需的学分数应为浮动学分.

For the -c argument I need to specify a subject and how many credits are required. The subject should be limited to a predefined list of subjects, and the number of credits required should be a float.

我可能可以使用子解析器执行此操作，但是因为它已经是子命令的一部分，所以我真的不希望事情变得更复杂.

I could probably do this with a subparser, but as it is this is already part of a sub-command so I don't really want things to get any more complicated.

推荐答案

您可以使用

---

例如，

---

For example,

% test.py -c foo 2
Namespace(credits=Credits(subject='foo', required=2.0))
foo
2.0
% test.py -c baz 2
ValueError: invalid subject 'baz'
% test.py -c foo bar
ValueError: could not convert string to float: bar

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