Python中的可迭代对象详解

>>> list1 = [1, 2, 3]
>>> for n in list1:
...     print(n)
...
1
2
3

>>> dict1 = {'one':1, 'two':2, 'three':3}
>>> for key in dict1.keys():
...     print(key)
...
one
two
three

from collections import Iterable

>>> isinstance([1,2,3], Iterable) # 列表为可迭代对象
True
>>> isinstance({1,2,3}, Iterable) # 集合为可迭代对象
True
>>> isinstance(100, Iterable) 
False

>>> from collections import Iterable

>>> class MyList(object):
...     def add(self, item):
...         self.container = []
...     def add(self, item):
...         self.container.append(item)
...     def __iter__(self):
...         """返回一个迭代器"""
...         # 暂时忽略如何构造一个迭代器对象
...         pass
...
>>> mylist = MyList()
>>> isinstance(mylist, Iterable) # mylist对象是一个可迭代对象
True

>>> list1 = [1, 2, 3]
>>> list1_iter = iter(list1)
>>> next(list1_iter)
1
>>> next(list1_iter)
2
>>> next(list1_iter)
3
>>> next(list1_iter)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration