在python中解析参数 [英] parsing argument in python

问题描述

我有一个问题，我正在努力寻找解决方案.我不确定我是否可以用 argparse 做到这一点.

I have a problem I am trying to find a solution. I am not sure if I can do it with argparse.

我希望能够指定一个选项

I want to be able to specify an option

myprog -a 1
myprog -a 2

现在当我有 a = 1 时，我希望能够指定 b 和 c.但是当a = 2时，我只能指定d.

Now when I have a = 1, I want to be able to specify b and c. But when a = 2, I can only specify d.

myprog -a 1 -b 3 -c 0
myprog -a 2 -d 3

还必须始终指定a

推荐答案

您不能将切换值作为单个 parse_args 调用执行此操作，但您可以执行以下操作之一:

You can't do this with switched values as a single parse_args call, but you can do one of:

1. 使用子命令/子解析器
2. 在完全配置解析器并在完整命令行上运行之前先做部分解析，首先只检查a，然后根据第一次调用的结果选择额外的解析器参数进行解析.诀窍是使用 parse_known_args 用于第一次调用，因此它处理 a(它可以识别)并忽略其他所有内容.

1. Use sub-commands/sub-parsers
2. Do partial parsing before fully configuring the parser and running on the complete command line, at first only checking for a, and then selecting the additional parser args to parse based on the result of the first call. The trick is to use parse_known_args for the first call, so it handles a (which it recognizes) and ignores everything else.

例如，对于方法#2，您可以这样做:

For example, for approach #2, you could do:

parser = argparse.ArgumentParser()
parser.add_argument('-a', required=True, type=int, choices=(1, 2)
args = parser.parse_known_args()

if args.a == 1:
    parser.add_argument('-b', ...)
    parser.add_argument('-c', ...)    
    args = parser.parse_args()
else:
    parser.add_argument('-d', ...)
    args = parser.parse_args()

这种方法的缺点是因错误使用而吐出的使用信息将不完整；您必须手动在基本解析器中包含指定真实"用法的文本，这并不有趣.子解析器无法根据值切换进行切换，但它们具有统一、连贯的用法显示.

Downside to this approach is that the usage info spat out for incorrect usage will be incomplete; you'd have to include the text specifying the "real" usage in the base parser manually, which is no fun. Subparsers can't be toggled based on value switches, but they have a unified, coherent usage display.

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