- 定义了__iter()__方法的类 是可迭代对象 ,需要返回一个迭代器对象的引用
- 定义了__iter()__,和__next()__方法的类是迭代器,__iter()__可以返回self,__next()__返回要迭代的元素,迭代完成抛出StopIteration异常以终止for循环
- eg:
class Reverse:
"""Iterator for looping over a sequence backwards."""
def __init__(self, data):
self.data = data
self.index = len(data)
def __iter__(self):
return self
def __next__(self):
if self.index == 0:
raise StopIteration
self.index = self.index - 1
return self.data[self.index]
>>> rev = Reverse('spam')
>>> iter(rev)
<__main__.Reverse object at 0x00A1DB50>
>>> for char in rev:
... print(char)
...
m
a
p
s