Parsing limited switches with python argparse

Question

Is there a way to parse only limited number of switches in a function using argparse? Say, my command is:

python sample.py -t abc -r dfg -h klm -n -p qui

And I want argparse to parse from -t to -h and leave the remaining, also show help for these only. Next I want to parse any switch after -h into another function and see corresponding help there.

Is this behavior possible in argparse? Also is there a way I can modify sys.arg it is using internally? Thanks.

Answer 1

python sample.py -t abc -r dfg -h klm -n -p qui

And I want argparse to parse from -t to -h and leave the remaining, also show help for these only. Next I want to parse any switch after -h into another function and see corresponding help there.

There are some issues with your specification:

Is -h the regular help? If so it has priority, producing the help without parsing the other arguments. The string after -h suggests you are treating it like a normal user define argument, which would then require initiating the parser with help turned off. But then how would you ask for help ?

What sets the break between the two parsings/help? The number of arguments, the -h flag (regardless of order), or the id of the flags. Remember argparse accepts flagged arguments in any order.

You could define one parser that knows about -t and -r , and another that handles -n and -p . Calling each with parse_known_args lets it operate without raising a unknown argument error.

You can also modify the sys.argv . parse_args (and the known variant), takes an optional argv argument. If that is none, then it uses sys.argv[1:] . So you could either modify sys.argv itself (deleting items), or you could pass a subset of sys.argv to the parser.

parser1.parse_known_args(sys.argv[1:5])
parser2.parse_known_args(['-n','one','-o','two'])
parser3.parse_args(sys.argv[3:])

Play with those ideas, and come back to us if there are further questions.

Answer 2

You can always modify sys.args and put anything you wish there.

As for your main question, you can have two parsers. One of them will have arguments -t to -h , the second -n and -p . Then you can use argparse 's parse_known_args() method on each parser, which will parse only the arguments defined for each of them.