字符串，列表，元组，字典，集合，生成器这些能通过for循环来遍历的数据类型都是可迭代对象
可通过isinstance判断是不是可迭代对象
>>> from collections import Iterable
>>> isinstance(‘Python‘, Iterable)
True
>>> isinstance([1,2,3], Iterable)
True
>>> isinstance((1,2,3), Iterable)
True
>>> isinstance({‘name‘:‘John‘,‘age‘:22}, Iterable)
True
>>> isinstance({1,2,3}, Iterable)
True
>>> isinstance((i*2 for i in range(10)), Iterable)
True
>>> isinstance(100, Iterable)
False
isinstance也可以判断是不是迭代器
>>> from collections import Iterator
>>> isinstance(‘Python‘, Iterator)
False
>>> isinstance([1,2,3], Iterator)
False
>>> isinstance((1,2,3), Iterator)
False
>>> isinstance({‘name‘:‘John‘,‘age‘:22}, Iterator)
False
>>> isinstance({1,2,3}, Iterator)
False
>>> isinstance((i*2 for i in range(10)), Iterator)
True
>>> isinstance(100, Iterator)
False
可见可迭代对象不一定是迭代器，但迭代器是可迭代对象
如果要把可迭代对象变为迭代器，可以使用iter()方法
>>> from collections import Iterator
>>> isinstance(iter(‘Python‘), Iterator)
True
>>> isinstance(iter([1,2,3]), Iterator)
True
>>> isinstance(iter((1,2,3)), Iterator)
True
>>> isinstance(iter({‘name‘:‘John‘,‘age‘:22}), Iterator)
True
>>> isinstance(iter({1,2,3}), Iterator)
True
迭代器可以用next()方法取数据，跟生成器一样
