Абстрактный адаптер аллюзий

class mumap:
    def __init__(self, proc, seq):
        self.__proc = proc
        self.__seq = seq
        self.__len__ = seq.__len__

    def __contains__(self, y):
        for val in self.__seq:
            if self.__proc(val) == y: return True
        return False

    def __eq__(self, y):
        if len(self) != len(y): return False
        i = iter(self.__seq)
        j = iter(y)
        try:
            if self._proc(i.next()) != j.next(): return False
        except StopIteration:
            return True

    def __getitem__(self, y): return self.__proc(self.__seq[y])
    def __getslice__(self, i, j): return mumap(self.__proc, self.__seq[i:j])
    def __iter__(self):
        i = iter(self.__seq)
        while True: yield self.__proc(i.next())
    def __str__(self): return ", ".join(self)


x = ["a","b"]

y = mumap(lambda x: x+"z", x)
print y
x[0]="g"
print y