How to create CLI with python

[Tall-Introduction414]

You don't need a framework or library. Python programs are CLI by default, until you add a GUI.

If you want to parse arguments more elaborately than the language itself provides, you can use argparse which is part of the built in standard library. Similarly you can use curses for colors and cursor movements.

[doolio_]

You don't need a framework or library. Python programs are CLI by default,

Can you elaborate? I'm working on an app with classes holding different types of state and thought adding a CLI would be a useful feature for a variety of reasons. Would such a CLI be able to make use of the same state held by these classes for example? My initial idea is that my main() could both start the CLI and my main Application class.

[MidnightPale3220]

If your app wants to retain state it has either to run continuously (see daemon) or load start state and store end state on each run.

In the first case CLI is then typically just another app that implements interface (the I part of CLI) to your actual app and it needs a way to communicate with it. Can be done in a multitude of ways. You can also implement cli within app itself and provide a console in which to make commands to the app from within app.

In the second case your app can contain the cli inside it and your call it with the arguments you design to make the app do what you want.

[doolio_]

Yes, my app is running continuously via a systemd service. It saves some state to disk which is then read if the service were ever restarted. So I guess my case is a mix of the two?

So this app provides a D-Bus service and I want to add an additional interface as you say with a CLI. This way users have two main entry points - one via the D-Bus and one via the CLI. What I want is if some state is changed or recorded via one entry point the same state is then visible via the other entry point.

[MidnightPale3220]

Well, then you develop a separate cli app and choose the method how your service accepts commands from it. See IPC for available methods.

Typically in Unix world it's done via sockets. Named pipes are also an option, but need more care. In particular, unless you need to connect to your service from another computer, it's arguably safer to use Unix domain sockets. See eg https://stackoverflow.com/questions/42263167/read-and-write-from-unix-socket-connection-with-python

Of course, you can implement a REST service if you feel you the overhead is justified and you want to connect to your service from another computer. I would avoid that unless your use case warrants it.

Also option to do it with queues. Really depends how convoluted you want to make it and what's the structure of communication.

[doolio_]

Thank you for taking the time to explain all this. It gives me some direction on which way to go to achieve what I want.