TypeError: iter() returned non-iterator of type 'SimpleCounter'

错误实例

# 1. 简单的迭代器
class SimpleCounter(object):
    def __init__(self, start, end):
        self.current = start
        self.end = end
    def __iter__(self):
        'returns itself as an iterator object'
        return self
    def next(self):
        'Returns the next value till current is lower than end'
        if self.current > self.end:
            raise StopIteration
        else:
            self.current += 1
            return self.current - 1
# # 2. 访问一
c = SimpleCounter(1, 3)
# print(c.next())
# print(c.next())
# print(c.next())
# # print(c.next())

# 3. 访问二
for entry in iter(c):
    print(entry)

修改：python3.0 中
迭代器的规则原来是发生了一些变化的。在新的迭代器规则中，迭代器对象应该实现__next__方法，而不是next

# 1. 简单的迭代器
class SimpleCounter(object):
    def __init__(self, start, end):
        self.current = start
        self.end = end
    def __iter__(self):
        'returns itself as an iterator object'
        return self
    def next(self):
        'Returns the next value till current is lower than end'
        if self.current > self.end:
            raise StopIteration
        else:
            self.current += 1
            return self.current - 1
# # 2. 访问一
c = SimpleCounter(1, 3)
print(c.next())
print(c.next())
print(c.next())
# print(c.next())

# 3. 访问二
#for entry in iter(c):
#    print(entry)