Implement event in Python

mokth

Implement event in Python, here is the code. Simple right ?

import sys
def _functionId(obj, nFramesUp):
    """ Create a string naming the function n frames up on the stack. """
    fr = sys._getframe(nFramesUp+1)
    co = fr.f_code
    return "%s.%s" % (obj.__class__, co.co_name)
def abstractMethod(obj=None):
    """ Use this instead of 'pass' for the body of abstract methods. """
    raise Exception("Unimplemented abstract method: %s" % _functionId(obj, 1))

# Interface class ( not really interface, cause python dont support interface yet)
class IEventListener:
    def fire(self, *args, **kargs):
        """ fire event        """
        abstractMethod(self)
   
    def perform(self, *args, **kargs):
        """ perform task        """
        abstractMethod(self)   

#Singleton base class        
class Singleton(object):
    _instance = None
    def __new__(cls, *args, **kwargs):
        if '_inst' not in vars(cls):
            cls._inst = object.__new__(cls, *args, **kwargs)
        return cls._inst

# Event class need to be singleton, act like manager here       
class Event(Singleton):
    def __init__(self):
        print "event init..."
        
        if self._instance ==None:
            self._instance =1
            self.handlers = set()
            
    def handle(self, handler):
        self.handlers.add(handler)
              
    def unhandle(self, handler):
        try:
            self.handlers.remove(handler)
        except:
            raise ValueError("Handler is not handling this event, so cannot unhandle it."
        
    def fire(self, *args, **kargs):
        self.perform( *args, **kargs)
        
    def perform(self, *args, **kargs):
        for handler in self.handlers:
            handler.fire(*args, **kargs)        
    def getHandlerCount(self):
        return len(self.handlers)
    __iadd__ = handle
    __isub__ = unhandle
    __call__ = fire
    __len__  = getHandlerCount

#Some sample Listener class
class Literner1(IEventListener):
    def __init__(self):
        Event().handle(self)  # Subcribe to event manager, any event, please notify me...
   
    #event manage will trigger this is any event fired.   
    def fire(self, *args, **kargs):
        self.perform( *args, **kargs)
        
    def perform(self, *args, **kargs):
        print "erform event in listener 1"

#Sample listener 2
class Literner2(IEventListener):
    def __init__(self):
        Event().handle(self)
        
    def fire(self, *args, **kargs):
        self.perform( *args, **kargs)
        
    def perform(self, *args, **kargs):
        print "erform event in listener 2"        
        
            
   
if __name__=='__main__':
    e1 =Event()
    e2= Event()
   
    l1 = Literner1()
    l2 = Literner2()
   
    e1.fire("1"
    e2.fire("1" # e1 and e2 are the same instance.