Python argparse:如何检测重复的可选参数? [英] Python argparse : how to detect duplicated optional argument?
问题描述
我正在使用带有可选参数的 argparse,但我想避免这样的事情:script.py -a 1 -b -a 2这里我们有两次可选参数'a',只返回第二个参数.我想获得两个值或获得错误消息.我应该如何定义论点?
I'm using argparse with optional parameter, but I want to avoid having something like this : script.py -a 1 -b -a 2 Here we have twice the optional parameter 'a', and only the second parameter is returned. I want either to get both values or get an error message. How should I define the argument ?
这是代码:
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('-a', dest='alpha', action='store', nargs='?')
parser.add_argument('-b', dest='beta', action='store', nargs='?')
params, undefParams = self.parser.parse_known_args()
推荐答案
append
action 将收集重复使用的值在一个列表中
append
action will collect the values from repeated use in a list
parser.add_argument('-a', '--alpha', action='append')
产生一个 args
命名空间,如:
producing an args
namespace like:
namespace(alpha=['1','3'], b='4')
解析后,您可以检查args.alpha
,并接受或抱怨值的数量.parser.error('repeated -a')
可用于发出 argparse 样式的错误消息.
After parsing you can check args.alpha
, and accept or complain about the number of values. parser.error('repeated -a')
can be used to issue an argparse style error message.
您可以在自定义 Action 类中实现类似的功能,但这需要了解此类类的基本结构和操作.我想不出任何可以在 Action 中完成的事情,也不能在之后的附加列表中完成.
You could implement similar functionality in a custom Action class, but that requires understanding the basic structure and operation of such a class. I can't think anything that can be done in an Action that can't just as well be done in the appended list after.
https://stackoverflow.com/a/23032953/901925 是一个无重复自定义的答案<代码>操作代码>.
https://stackoverflow.com/a/23032953/901925 is an answer with a no-repeats custom Action
.
为什么要使用带有标记参数的 nargs='?'
像这样?如果没有 const
参数,这几乎是无用的(请参阅文档中的 nargs=?
部分).
Why are you using nargs='?'
with flagged arguments like this? Without a const
parameter this is nearly useless (see the nargs=?
section in the docs).
另一个类似的 SO:Python argparse 与 nargs 行为不正确
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