Terminal Interfaces in Python

Although there is a fair choice of GUI libraries for Python (good overview of Python GUI libraries is here), sometimes we need just a little bit more enhanced terminal interface, like in my recent project –  XMPP test client  – where requirements were quite simple – just to split terminal screen into two areas –  main screen where messages are displayed (possibly asynchronously) and bottom line, where commands/messages can  be entered:


In Python we have couple of options for terminal UI programming:

  • curses – curses library is part of standard python distribution, it provides lower level access to terminal programming and terminal control sequences.  Many things are left to users – like resizing UI, event loops etc.
  • urwid – is an excellent external library, which provides higher level interfaces for programming terminal UIs. It’s a bit similar to above mentioned GUI kits, providing widgets, layout managers, event loop etc.  And many common tasks missing in curses are already included.

I decided to use urwid, because it looked easier to start with and many required functionalities  were already provided (like already mentioned resizing, which I think would be pretty tedious to re-implement in curses).  I’ve created simple commander module, which provides interface similar to build-in cmd.Cmd, but with UI layout as shown above.   With this module we can create simple tools very easily:

if __name__=='__main__':
    class TestCmd(Command):
        def do_echo(self, *args):
            '''echo - Just echos all arguments'''
            return ' '.join(args)
        def do_raise(self, *args):
            raise Exception('Some Error')
    c=Commander('Test', cmd_cb=TestCmd())
    #Test asynch output -  e.g. comming from different thread
    import time
    def run():
        while True:
            c.output('Tick', 'green')
    #start main loop

Which creates tool like this:


6 thoughts on “Terminal Interfaces in Python”

  1. When I pressed UP key, the texts in the input bar at the bottom of the terminal changes to last command I typed, as was expected. But, the cursor appears at the beginning of the line, and I want it to be at the ending of the line. Any ways to do that?

    I’m a Chinese native speaker, never mind if there are errors in this comment 😉

    Thank you very much!

      1. I should read your code before asking the question… I’m sorry that I had not noticed your reply ‘coz I thought I will be notified (via Email). However, thank you very much, that worked!

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