python - argparse 选择允许值的结构

Question

使用关于 Python dependencies between groups using argparse 的 argparse ，我有一个解析器的某个解析器组的参数部分 - 例如:

group_simulate.add_argument('-P',
                            help='simulate FC port down',
                            nargs=1,
                            metavar='fc_port_name',
                            dest='simulate')

如何使用 choices将选择限制为下一个结构的参数列表:

1:m:"number between 1 and 10":p:"number between 1 and 4"

我曾尝试使用范围选项，但找不到创建可接受的选择列表的方法

例子:合法参数:

test.py -P 1:m:4:p:2

不合法的参数:

test.py -P 1:p:2
test.py -P abvds

非常感谢大家的帮助!

Answer 1

您可以定义一个自定义类型，如果字符串与您需要的格式不匹配。

def SpecialString(v):
    fields = v.split(":")
    # Raise a value error for any part of the string
    # that doesn't match your specification. Make as many
    # checks as you need. I've only included a couple here
    # as examples.
    if len(fields) != 5:
        raise argparse.ArgumentTypeError("String must have 5 fields")
    elif not (1 <= int(fields[2]) <= 10):
        raise argparse.ArgumentTypeError("Field 3 must be between 1 and 10, inclusive")
    else:
        # If all the checks pass, just return the string as is
        return v

group_simulate.add_argument('-P',
                        type=SpecialString,
                        help='simulate FC port down',
                        nargs=1,
                        metavar='fc_port_name',
                        dest='simulate')

更新:这里有一个完整的自定义类型来检查值。所有检查完成在正则表达式中，虽然它只给出一条一般性错误消息如果任何部分是错误的。

def SpecialString(v):
    import re  # Unless you've already imported re previously
    try:
        return re.match("^1:m:([1-9]|10):p:(1|2|3|4)$", v).group(0)
    except:
        raise argparse.ArgumentTypeError("String '%s' does not match required format"%(v,))