创建自己的迭代器

# -*- coding: utf-8 -*-'''创建自己的迭代器类，需要实现两个方法:1. __iter__: The iter method simply returns a reference to the object itself and is always implemented to do so.2. __next__: '''class _BagIterator:        def __init__(self, theList):        self._bagItems = theList        self._curItem = 0    def __iter__(self):        return self    def __next__(self):        if self._curItem < len(self._bagItems):            item = self._bagItems[self._curItem]            self._curItem += 1            return item        else:            raise StopIteration