Argparser's one subparser for two different commands

Question

I have this three types of commands in code:

test.py save file_name
test.py load file_name
test.py list_files

Currently, to parse them i use three subparsers, but is there opportunity to use one subparser to two commads 'load' and 'save', because they use same argument 'file_name'?

parser = argparse.ArgumentParser(description='Test parser')
subparsers = parser.add_subparsers(dest='command')

parser_load = subparsers.add_parser("load")
parser_load.add_argument("file_name")

parser_save = subparsers.add_parser("save")
parser_save.add_argument("file_name")

parser_list_files = subparsers.add_parser("list_files")

I've never done this myself, but I found this question after a quick search and it looks promising: [Add argument to multiple subparsers](https://stackoverflow.com/q/7498595/4518341) — wjandrea, Mar 26 '21 at 23:09
What's wrong with the code you show? You've already done the hard work of typing both cases :) But you could try making `save` an alias for `load`. I think the alias will appear as the `command` value (but check). — hpaulj, Mar 26 '21 at 23:14

score 0 · Answer 1 · answered Mar 27 '21 at 02:23

If the two commands are identical, they can be aliases of the same parser

In [6]: parser = argparse.ArgumentParser()
In [7]: sp = parser.add_subparsers(dest='cmd')
In [8]: sp1 = sp.add_parser('load', aliases=['store'])
In [9]: sp1.add_argument('test');

In [10]: parser.parse_args('load foo'.split())
Out[10]: Namespace(cmd='load', test='foo')

In [12]: parser.parse_args('store foo'.split())
Out[12]: Namespace(cmd='store', test='foo')

The alias appears in the namespace.

In [13]: parser.print_help()
usage: ipython3 [-h] {load,store} ...

positional arguments:
  {load,store}

optional arguments:
  -h, --help    show this help message and exit

But if you prefer to keep them separate, there are various ways to ease your typing burden.

There's copy-n-paste
There's the parents mechanism, cute but limited.
Or use one or more utility functions to create multiple subparsers.

The Perl inventor claimed programmers are lazy, going to great lengths to avoid typing repetitive code. http://threevirtues.com/

Argparser's one subparser for two different commands

1 Answers1