python必备内置函数- iter(object, sentinel)

返回一个可迭代对象, sentinel可省略

In [72]: lst = [1,3,5]

In [73]: for i in iter(lst):
    ...:     print(i)
    ...:
1
3
5

sentinel 理解为迭代对象的哨兵，一旦迭代到此元素，立即终止：

In [81]: 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,which 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 [82]: t = TestIter() ...: t1 = iter(t, 3) ...: for i in t1: ...: print(i) ...: call is called,which would return 1 1 call is called,which would return 3