【009】Python迭代器对象减少开销

Aojacy

'''
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
'''

import requests
from collections.abc import Iterator,Iterable

class weatherIterator(Iterator):
    def __init__(self,cities):
        self.cities = cities
        self.index = 0
    def getweather(self,city):
        r = requests.get(r'http://wthrcdn.etouch.cn/weather_mini?city='+city)
        data = r.json()['data']['forecast'][0]
        return '%s: %s ,%s' % (city,data['low'],data['high'])
    def __next__(self):
        if self.index == len(self.cities):
            raise StopIteration
        city = self.cities[self.index]
        self.index += 1
        return self.getweather(city)

class weatherIterable(Iterable):
    def __init__(self,cities):
        self.cities = cities
    def __iter__(self):
        return weatherIterator(self.cities)

for x in weatherIterable(['北京','上海','南京']):
    print(x)
'''
提问与思考：
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，
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
'''