[Python-Dev] New Module: CommandLoop

[Crutcher Dunnavant]

This is something I've been working on for a bit, and I think it is
more or less ready to bring up on this list. I'd like to add a module
(though probably not for 2.5).

Before you ask, this module is _not_ compatible with cmd.py, as it is
command oriented, whereas cmd.py is line oriented.

Anyway, I'm looking for feedback, feature requests before starting the
submission process.

Code available here:
http://littlelanguages.com/web/software/python/modules/cmdloop.py

Base class for writing simple interactive command loop environments.

CommandLoop provides a base class for writing simple interactive user
environments.  It is designed around sub-classing, has a simple command
parser, and is trivial to initialize.

Here is a trivial little environment written using CommandLoop:

    import cmdloop

    class Hello(cmdloop.commandLoop):
        PS1='hello>'

        @cmdloop.aliases('hello', 'hi', 'hola')
        @cmdloop.shorthelp('say hello')
        @cmdloop.usage('hello TARGET')
        def helloCmd(self, flags, args):
            '''
            Say hello to TARGET, which defaults to 'world'
            '''
            if flags or len(args) != 1:
                raise cmdloop.InvalidArguments
            print 'Hello %s!' % args[0]

        @cmdloop.aliases('quit')
        def quitCmd(self, flags, args):
            '''
            Quit the environment.
            '''
            raise cmdloop.HaltLoop

    Hello().runLoop()

Here's a more complex example:

    import cmdloop

    class HelloGoodbye(cmdloop.CommandLoop):
        PS1='hello>'

        def __init__(self, default_target = 'world'):
            self.default_target = default_target
            self.target_list = []

        @cmdloop.aliases('hello', 'hi', 'hola')
        @cmdloop.shorthelp('say hello')
        @cmdloop.usage('hello [TARGET]')
        def helloCmd(self, flags, args):
            '''
            Say hello to TARGET, which defaults to 'world'
            '''
            if flags or len(args) > 1:
                raise cmdloop.InvalidArguments
            if args:
                target = args[0]
            else:
                target = self.default_target
            if target not in self.target_list:
                self.target_list.append(target)
            print 'Hello %s!' % target

        @cmdloop.aliases('goodbye')
        @cmdloop.shorthelp('say goodbye')
        @cmdloop.usage('goodbye TARGET')
        def goodbyeCmd(self, flags, args):
            '''
            Say goodbye to TARGET.
            '''
            if flags or len(args) != 1:
                raise cmdloop.InvalidArguments
            target = args[0]
            if target in self.target_list:
                print 'Goodbye %s!' % target
                self.target_list.remove(target)
            else:
                print "I haven't said hello to %s." % target

        @cmdloop.aliases('quit')
        def quitCmd(self, flags, args):
            '''
            Quit the environment.
            '''
            raise cmdloop.HaltLoop

        def _onLoopExit(self):
            if len(self.target_list):
                self.pushCommands(('quit',))
                for target in self.target_list:
                    self.pushCommands(('goodbye', target))
            else:
                raise cmdloop.HaltLoop

    HelloGoodbye().runLoop()

--
Crutcher Dunnavant <crutcher at gmail.com>
littlelanguages.com
monket.samedi-studios.com