''' example of an iterator ''' 

class MyClass:    
    def __init__(self):
        self.data = [1,2,3]
        
    def __iter__(self):
        self.pos = len(self.data)
        return self
    
    def next(self):        
        if self.pos > 0:
            self.pos = self.pos-1
            return self.data[self.pos]
        else:
            raise StopIteration