python迭代器

'''
判断是否可迭代
字符串、列表、元组、字典、集合都可以被for循环，说明他们都是可迭代的
'''
from collections.abc import Iterable
l = [1, 2, 3, 4]
t = (1, 2, 3, 4)
d = {1: 2, 3: 4}
s = {1, 2, 3, 4}

print(isinstance(l, Iterable))
print(isinstance(t, Iterable))
print(isinstance(d, Iterable))
print(isinstance(s, Iterable))

'''
可迭代的内部实现了__iter__方法
'''
print('__iter__' in dir([1,2]))
print('__iter__' in dir((2,3)))
print('__iter__' in dir({1:2}))
print('__iter__' in dir({1,2}))

iter_l = [1,2,3,4,5,6].__iter__()
#获取迭代器中元素的长度
print(iter_l.__length_hint__())
#根据索引值指定从哪里开始迭代
print('*',iter_l.__setstate__(4))
#一个一个的取值
print('**',iter_l.__next__())
print('***',iter_l.__next__())