0

I would like to parse an optional argument with multiple values with docopt. Below is the example usage.

my_program.py --loc pcg acc
# or anything that achieve similar result

and after parsing, I expect that to have a python list like so

arguments["--loc"] = ["pcg", "acc"]

I browsed around and found out if this is doable in argparse by passing nargs argument.

I couldn't find any similar way in docopt, is this doable in docopt? If not, what's the alternative?

An alternative that I can think of is to ask user specify value separated by comma and manually split it during parsing as below.

my_program.py [--loc=<comma_separated_str>]

In the python code

locs = arguments["--loc"].split(",") if arguments["--loc"] else []

However, that seems ugly, so I'm looking for a proper way to do so with docopt.

Darren Christopher
  • 3,893
  • 4
  • 20
  • 37

2 Answers2

1

One approach would be to use the elipsis (...) operator, so that an option can be repeated zero or more times with square brackets, or one or more times with parenthesis . For example

"""Usage: my_program.py --help
       my_program.py [--loc=<loc>]...
"""

from docopt import docopt
print(docopt(__doc__))

would give the following output

$ python my_program.py --loc=pcg --loc=acc
{'--help': False,
 '--loc': ['pcg', 'acc']}
J. P. Petersen
  • 4,871
  • 4
  • 33
  • 33
0

The definition you are looking for is probably

"""
Usage: my_program.py --help
   my_program.py [(--loc <loc>) [<loc>...]]
"""

from docopt import docopt
print(docopt(__doc__))

Multiple --loc values are provided with spaces between them

python3 my_program.py --loc pcg acc hah
{'--help': False,
 '--loc': True,
 '<loc>': ['pcg', 'acc', 'hah']}

The --loc argument is indeed optional

$ python3 my_program.py
{'--help': False,
 '--loc': False,
 '<loc>': []}

Providing no values for --loc results in an error

$ python3 my_program.py --loc
Usage: my_program.py --help
       my_program.py [(--loc <loc>) [<loc>...]]

If --loc could be used without any value, this simpler definition will do

"""
Usage: my_program.py --help
       my_program.py [--loc <loc> ...]
"""

from docopt import docopt
print(docopt(__doc__))

resulting in

$ python3 my_program.py --loc
{'--help': False,
 '--loc': True,
 '<loc>': []}

It is otherwise equivalent to the first definition

user368683
  • 360
  • 3
  • 7