Python Argparse append with nargs= >1 -

so trying create parser can take arbitrary list of choices (things plot), optional parameters specified each choice. , have eschewed idea of sub-subparsers using multiple arguments of form:

--plot foo --xlim 0 10 --ylim -5 5 --plot bar --xlim -5 5 --ylim 0 10 --clim 1e24 1e27 

but can't seem append action work nargs=2:

>>> import argparse >>> parser = argparse.argumentparser() >>> parser.add_argument('--foo', action='append', nargs=2, type=int) _appendaction(option_strings=['--foo'], dest='foo', nargs=2, const=none, default=none,  type=<type 'int'>, choices=none, help=none, metavar=none) >>> parser.parse_args("--foo 1 2 --foo 3 4") usage: [-h] [--foo foo foo] : error: unrecognized arguments: - - f o o   1   2   - - f o o   3 4 

i hoping list of lists or list of tuples. is desired behaviour unsupported argparse or doing wrong in implementation?

you should pass list of strings, not string:

>>> import argparse >>> parser = argparse.argumentparser() >>> parser.add_argument('--foo', action='append', nargs=2, type=int) _appendaction(option_strings=['--foo'], dest='foo', nargs=2, const=none, default=none, type=<type 'int'>, choices=none, help=none, metavar=none) >>> parser.parse_args(["--foo", "1", "2", "--foo", "3", "4"])  # <---- namespace(foo=[[1, 2], [3, 4]])