Stuff

def CombinationEnumerator(listObj, selection) :
    class CombEnum(object) :
        def __init__(self, listObj, selection) :
            assert selection <= len(listObj)
            self.items = listObj
            self.route = ([True, ]*selection) + [False, ]*(len(listObj)-selection)
            self.selection = selection
        def value(self) :
            result = [ val for flag, val in zip(self.route, self.items) if flag ]
            return result
        def next(self) :
            try :
                while self.route[-1] :
                    self.route.pop()
                while not self.route[-1] :
                    self.route.pop()
            except :
                return False

            self.route[-1] = False

            count = self.route.count(True)
            self.route.extend( (self.selection - count) * [True,] )
            padding = len(self.items) - len(self.route)
            self.route.extend( padding * [False, ])
            return True

    if selection == 0 :
        yield []
        return

    rotor = CombEnum(listObj, selection)
    yield rotor.value()
    while rotor.next() :
        yield rotor.value()