【009】Python迭代器对象减少开销

Aojacy

1. '''
   
2. 目的：通过迭代器对象将需要信息存储到一个对象，并实时显示，减小时间和空间开销
   
3. '''
   
4. 
   
5. import requests
   
6. from collections.abc import Iterator,Iterable
   
7. 
   
8. class weatherIterator(Iterator):
   
9.     def __init__(self,cities):
   
10.         self.cities = cities
    
11.         self.index = 0
    
12.     def getweather(self,city):
    
13.         r = requests.get(r'http://wthrcdn.etouch.cn/weather_mini?city='+city)
    
14.         data = r.json()['data']['forecast'][0]
    
15.         return '%s: %s ,%s' % (city,data['low'],data['high'])
    
16.     def __next__(self):
    
17.         if self.index == len(self.cities):
    
18.             raise StopIteration
    
19.         city = self.cities[self.index]
    
20.         self.index += 1
    
21.         return self.getweather(city)
    
22. 
    
23. class weatherIterable(Iterable):
    
24.     def __init__(self,cities):
    
25.         self.cities = cities
    
26.     def __iter__(self):
    
27.         return weatherIterator(self.cities)
    
28. 
    
29. for x in weatherIterable(['北京','上海','南京']):
    
30.     print(x)
    
31. '''
    
32. 提问与思考：
    
33. 1、for循环工作机制：可迭代对象通过调用自身的__iter__()方法生成迭代器，
    
34. 迭代器对象通过__next__()方法，进行迭代访问，迭代完毕最后抛出异常StopIteration
    
35. '''

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