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[SOLVED] How to decide what to do with command line parameters? (programming.dev)

submitted 1 year ago* (last edited 1 year ago) by [email protected] to c/[email protected]

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This is solved, I was being dumb. Please see second EDIT below

This isn't really language specific, but if it helps I'm using Python. I can get the parameters just fine with the Traitlets module, but I'm still a novice really and figuring out which patterns to use is challenging.

Say you have a bunch of command line parameters. Some are booleans, where their presence means True, absence means False. Other parameters must accept one text string, and others can be used multiple times to build a list of strings.

It feels inefficient/wrong to use a bunch of IF/THEN/ELSE statements to decide what to do with the parameters, and prone to edge case errors. Is there a pattern that would invoke the correct method based on the combination of input parameters?

Examples:

app thing --dry-run --create --name=newname01 --name=newname02 --verbose

app thing --create --name=newname01 --name=newname02 --name=newname03

app job --cancel -i 01 -i 02 -i 03

EDIT: Via the Traitlets module, I get those arguments parsed and accessible as self.argname, so getting them into my app is working great. It's just deciding what to do with them that is confusing me.

Thank you, sorry for my noobness.

EDIT2: I think I understand where I'm going wrong:

I'm creating subcommands based on objects, not actions. i.e. appname thing --action should really be appname action --thing. Once things are divided up into actions, assigning things to those actions will be much, much easier and straightforward.

Sorry for a confusing and fairly pointless post :(

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[–] [email protected] 2 points 1 year ago (1 children)

Others have already mentioned argparse, which is a pretty great module for argument parsing if you want to use something built-in. If you're willing to look into other libraries though, I'd recommend taking a look at Click. You should be able to pip install click to use it. It takes advantage of defining the CLI through decorators, and from my experience, works better when you want to have subcommands.

[–] [email protected] 2 points 1 year ago

Interesting! I'll check it out.

I've replaced the Traitlets based arg parsing with argparse, and the subcommands are working ok so far. I'll see if Click can add anything, thank you for the recommendation!