Basic Command Bus example

commandbus.py

import inspect


class HandlerNotFound(Exception):
    pass


class BasicCommandBus(object):
    
    def execute(self, command):
        self._determine_handler(command).execute(command)
    
    def _determine_handler(self, command):
        command_module = inspect.getmodule(command)
        command_type_name = type(command).__name__.split('Command')[0]
        possible_handler_name = "{0}Handler".format(command_type_name)
        
        handler = getattr(command_module, possible_handler_name, None)
        
        if handler is None:
            raise HandlerNotFound("Handler not found for {0}".format(command_type_name))
        
        return handler()

example.py

from commandbus import BasicCommandBus
from hello import HelloPersonCommand

bus = BasicCommandBus()
bus.execute(HelloPersonCommand(receiver="fred", sender="fred") # prints out "Fred says: Hello Fred!"

hello.py

from collections import namedtuple

HelloPersonCommand = namedtuple("HelloPersonCommand", ["receiver", "sender"])

class HelloPersonHandler(object):
    def execute(self, command):
        print("{0.sender} says: Hello {0.receiver}!".format(command))