53
编辑日期: 2024-11-28 文章阅读: 次
@author jackzhenguo
@desc
@date 2019/3/8
53 创建迭代器
使用iter(obj, sentinel), 返回一个可迭代对象, sentinel可省略(一旦迭代到此元素，立即终止)
In [1]: lst = [1,3,5]
In [2]: for i in iter(lst):
...: print(i)
...:
1
3
5
In [1]: class TestIter(object):
...: def __init__(self):
...: self.l=[1,3,2,3,4,5]
...: self.i=iter(self.l)
...: def __call__(self): #定义了__call__方法的类的实例是可调用的
...: item = next(self.i)
...: print ("__call__ is called,fowhich would return",item)
...: return item
...: def __iter__(self): #支持迭代协议(即定义有__iter__()函数)
...: print ("__iter__ is called!!")
...: return iter(self.l)
In [2]: t = TestIter()
In [3]: t() # 因为实现了__call__，所以t实例能被调用
__call__ is called,which would return 1
Out[3]: 1
In [4]: for e in TestIter(): # 因为实现了__iter__方法，所以t能被迭代
...: print(e)
...:
__iter__ is called!!
1
3
2
3
4
5
