argparse:让相同的必需参数是位置或可选的 [英] argparse: let the same required argument be positional OR optional

问题描述

我希望将必需的命令行参数作为位置参数或可选参数传递.例如，我希望从以下任何调用中执行相同的操作:

I would like to have a required command line argument passed as a positional argument or an optional argument. For example, I would like the same action be performed from any of the following invocations:

prog 10
prog -10
prog -n 10
prog --num 10

这可以通过 argparse 实现吗?

Is this possible with argparse?

推荐答案

使用互斥组我可以创建一个合理的近似:

With a mutually exclusive group I can create a reasonable approximation:

在交互式会话中:

In [10]: parser=argparse.ArgumentParser()
In [11]: grp=parser.add_mutually_exclusive_group(required=True)
In [12]: a=grp.add_argument('pos',nargs='?',type=int,default=0)
In [13]: b=grp.add_argument('-n','--num')

grp 可以包含任意数量的可选和一个可选的位置.我为位置选择了不同的 type 只是为了突出差异.

grp can contain any number of optionals, and one optional positional. I chose a different type for the positional just a highlight the difference.

只是位置值:

In [14]: parser.parse_args(['10'])
Out[14]: Namespace(num=None, pos=10)

各种形式的可选:

In [16]: parser.parse_args(['-n10'])
Out[16]: Namespace(num='10', pos=0)
In [17]: parser.parse_args(['--num=10'])
Out[17]: Namespace(num='10', pos=0)
In [18]: parser.parse_args(['--num','10'])
Out[18]: Namespace(num='10', pos=0)

测试组独占性

In [25]: parser.parse_args(['--num=20','10'])
usage: ipython3 [-h] [-n NUM] [pos]
ipython3: error: argument pos: not allowed with argument -n/--num

和需要的组:

In [26]: parser.parse_args([])
usage: ipython3 [-h] [-n NUM] [pos]
ipython3: error: one of the arguments pos -n/--num is required

我尝试为位置提供与可选相同的 dest - 这样两者都会写入 num.但这会导致位置覆盖使用默认值写入 dest(如果需要，我可以添加详细信息)

I experimented with giving the positional the same dest as the optional - so both would write to num. But this results in the positional over writing the dest with its default (I can add details if needed)

In [19]: a.dest
Out[19]: 'pos'
In [20]: a.dest='num'
In [21]: parser.parse_args(['--num','10'])
Out[21]: Namespace(num=0)

后解析代码必须以任何有意义的方式处理 args.pos 和 args.num 值.

Post parsing code will have to handle the args.pos and args.num values in what ever way makes sense.

'-10' 输入无法处理.好吧，我可以定义:

The '-10' input is impossible to handle. Well, I could define:

parser.add_argument('-1')

但结果可能不是你想要的:

but the result is probably not what you want:

In [31]: parser.parse_args(['--num=20','-12'])
Out[31]: Namespace(1='2', num='20', pos=0)

总的来说，这个要求给程序员带来了不必要的困难.

Overall this requirement makes things unnecessarily difficult for you the programmer.

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