plugins pattern + sub command

Question

I will do a command line application with plugin capability, each new plugin will be invoked by a sub command from a __main__.py script.

I used to use argparse, I wonder if it's possible with argparse to implement sub command + plugin looking like (I found some tool but using deprecated packages) ?

myfantasticCLI ├── __main__.py └── plugins ├── create.py ├── notify.py └── test.py

I know that I could use argparse for sub command, but don't know how to use it in a dynamic loading way. :/

hpaulj · Accepted Answer · 2016-05-02 16:34:30Z

If you initialize the argparse subparsers with

sp = parser.add_subparsers(dest='cmd',...)

then after parsing args.cmd will be the name of the chosen subparser or command.

Then a simple if tree could import and run the desired modules

cmd = args.cmd if cmd in ['module1',...]: import plugins.module1 as mod: mod.run(...) elif cmd in ['module2',....]: import plugins.module2 as mod: ...

There are fancier ways of doing this, but I prefer starting with the obvious.

Also my focus is on getting the cmd name from the parser, not on the details of importing a module given the name. You don't need argparse to test the import given a name part of the problem.

Sounds great but, that implies explicit import. I would like to build something plugins based stackoverflow.com/questions/932069/….
If all you need from argparse is the name of the plugin to import, the subparsers mechanism may be too much. Any string argument would work. You could even collect the allowable names in a choices parameter.

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