python爬取的数据怎么保存成json格式？能提供完整代码吗》我太笨了，一直搞不好

import requests
from bs4 import BeautifulSoup
# 自定义函数，获取城市的AQI
def get_city_aqi(city_pinyin):
    url = 'http://pm25.in/' + city_pinyin
    r = requests.get(url, timeout=300)
    # 创建BeautifulSoup对象
    soup = BeautifulSoup(r.text, 'html.parser')
    # 按照属性查找所有满足条件的节点
    div_list = soup.find_all('div', {'class': 'span1'})

    city_aqi = []
    for i in range(8):
        div_content = div_list[i]
        caption = div_content.find('div', {'class': 'caption'}).text.strip()
        value = div_content.find('div', {'class': 'value'}).text.strip()
        # 将每一对caption和value作为一个元素增加到列表中
        city_aqi.append((caption, value))

    return city_aqi
# 自定义函数：获取所有的城市列表
def get_all_cities():
    url = 'http://pm25.in/'
    city_list = []
    r = requests.get(url)
    soup = BeautifulSoup(r.text, 'html.parser')
    city_div = soup.find_all('div', {'class': 'bottom'})[1]
    city_link_list = city_div.find_all('a')
    for city_link in city_link_list:
        # 获取每个城市的名称
        city_name = city_link.text
        # 获取每个城市的拼音
        city_pinyin = city_link['href'][1:]
        # 将每对城市名称和城市拼音作为一个元素写入城市列表中
        city_list.append((city_name, city_pinyin))
    return city_list
def main():
    # 调用自定义函数，获取所有城市列表
    city_list=get_all_cities()
    for city in city_list:
        city_name = city[0]
        city_pinyin = city[1]
        # 调用自定义函数，获取每个城市的AQI值
        city_aqi = get_city_aqi(city_pinyin)
        print(city_name, city_aqi)
if __name__ == '__main__':
    main()