可迭代对象、迭代器和生成器

可迭代对象和迭代器:

 1 """
 2 可迭代对象包括迭代器、序列(字符串、列表、元组)和字典
 3 可迭代对象:要么实现__iter__方法,返回该可迭代对象的迭代器类实例,要么实现了__getitem__方法,并且参数是从零开始的索引
 4 迭代器:实现了__iter__方法,返回迭代器本身,且实现了__next__方法,返回下一个元素,若没有元素抛出StopIteration异常
 5 """
 6 
 7 
 8 class MyList(object):                       # 定义可迭代对象类(__iter__方法)
 9     def __init__(self, num):
10         self.data = num
11 
12     def __iter__(self):
13         return MyListIterator(self.data)    # 返回该可迭代对象的迭代器类实例
14 
15 
16 class MyListIterator(object):              # 定义迭代器类(__iter__方法和__next__方法)
17     def __init__(self, data):
18         self.data = data
19         self.now = 0
20 
21     def __iter__(self):
22         return self                         # 返回迭代器本身
23 
24     def __next__(self):
25         while self.now < self.data:
26             self.now += 1
27             return self.now-1               # 返回下一个元素
28         raise StopIteration
29 
30 
31 def main():
32     my_list = MyList(5)
33     print(type(my_list))
34 
35     my_list_iter = iter(my_list)
36     print(type(my_list_iter))
37 
38     for i in my_list:
39         print(i)
40 
41 
42 if __name__ == '__main__':
43     main()
44 
45 """
46 结果:
47 <class '__main__.MyList'>
48 <class '__main__.MyListIterator'>
49 0
50 1
51 2
52 3
53 4
54 """

生成器:

 1 """
 2 生成器:一种特殊的迭代器,自动实现了“迭代器协议”(__iter__和__next__方法)
 3 """
 4 
 5 
 6 def my_generator(num):                  # 定义生成器
 7     now = 0
 8     while now < num:
 9         temp = (yield now)
10         now = now + 1 if temp is None else temp
11 
12 
13 def main():
14     my_gen = my_generator(5)
15     print(type(my_gen))
16     print(dir(my_gen))                    # 返回该对象拥有的方法名
17 
18     print(next(my_gen))
19     print(next(my_gen))
20 
21     my_gen.send(3)                        # 重置当前迭代值
22     print("my_gen.send(3)")
23     print(next(my_gen))
24 
25 
26 if __name__ == '__main__':
27     main()
28 
29 """
30 结果:
31 <class 'generator'>
32 ['__class__', '__del__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__lt__', '__name__', '__ne__', '__new__', '__next__', '__qualname__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'close', 'gi_code', 'gi_frame', 'gi_running', 'gi_yieldfrom', 'send', 'throw']
33 0
34 1
35 my_gen.send(3)
36 4
37 """

 

posted @ 2020-11-12 18:53  甜了酒了果  阅读(120)  评论(0编辑  收藏  举报