New Module: CommandLoop

[Crutcher]

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()