Python爬虫学习第三章-4.3-使用xpath解析爬取全国城市名称

  这一节主要是使用xpath解析爬取全国城市名称

这里使用的网址是：空气质量历史数据查询

  这一个案例体现的点主要是xpath表达式中的’|’。

思路：

• 一种思路是：因为城市分布在热门城市和全部城市这两部分中，所以可以设计两个xpath表达式进行数据解析得到城市名称所在的a标签。

  其实两个xpath表达式分别是hot_li_list = tree.xpath('//div[@class="bottom"]/ul/li')和city_names_list = tree.xpath('//div[@class="bottom"]/ul/div[2]/li')

• 另一种思路是使用一个xpath表达式解析到所有城市的a标签，

  具体为a_list = tree.xpath('//div[@class="bottom"]/ul/li/a | //div[@class="bottom"]/ul/div[2]/li/a')，注意两个xpath表达式之间用’|'分开。

  当然，总的流程还是先指定url并进行UA伪装，有参数的话进行参数处理，发送请求并获取响应数据；然后利用xpath表达式进行数据解析，设计xpath表达式批量获取想要信息所在的具体的标签，在这个案例中就是a标签；然后用循环，在循环中再使用xpath表达式，用/text()、//text()获取内容或者用/@属性名称获取属性。最后进行保存即可。

使用第一种思想的源代码：

import requests
from lxml import etree
if __name__=="__main__":
    # 使用xpath进行数据解析的步骤：先实例化一个etree类的的对象，并且需要将被解析的页面源码数据加载到该对象中
    # 先爬取网页源码数据
    url = "https://www.aqistudy.cn/historydata/"
    headers = {
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.121 Safari/537.36'
    }
    page_text = requests.get(url = url,headers=headers).text

    tree = etree.HTML(page_text)
    hot_li_list = tree.xpath('//div[@class="bottom"]/ul/li')
    all_city_names = []
    #解析到了热门城市的城市名称
    for li in hot_li_list:
        hot_city_name = li.xpath('./a/text()')[0]
        all_city_names.append(hot_city_name)

    #解析的是全部城市的名称
    city_names_list = tree.xpath('//div[@class="bottom"]/ul/div[2]/li')
    for li in city_names_list:
        city_name = li.xpath('./a/text()')[0]
        all_city_names.append(city_name)
    print(all_city_names)
    print(len(all_city_names))

使用第二种思想的源代码：

import requests
from lxml import etree
if __name__=="__main__":
    # 使用xpath进行数据解析的步骤：先实例化一个etree类的的对象，并且需要将被解析的页面源码数据加载到该对象中
    # 先爬取网页源码数据
    #使用改进的xpath表达式一次性的爬取到热门城市和全部城市
    url = "https://www.aqistudy.cn/historydata/"
    headers = {
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.121 Safari/537.36'
    }
    page_text = requests.get(url=url, headers=headers).text

    tree = etree.HTML(page_text)
    #想要解析到热门城市和所有城市对应的a标签
    #热门城市对应的a标签的层级关系是：//div[@class="bottom"]/ul/li/a  ；
    #所有城市对应的a标签的层级关系是：//div[@class="bottom"]/ul/div[2]/li/a
    a_list = tree.xpath('//div[@class="bottom"]/ul/li/a | //div[@class="bottom"]/ul/div[2]/li/a')
    all_city_names = []
    for a in a_list:
        city_name = a.xpath('./text()')
        all_city_names.append(city_name)
    print(all_city_names)
    print(len(all_city_names))

结果：

[['北京'], ['上海'], ['广州'], ['深圳'], ['杭州'], ['天津'], ['成都'], ['南京'], ['西安'], ['武汉'], ['阿坝州'], ['安康'], ['阿克苏地区'], ['阿里地区'], ['阿拉善盟'], ['阿勒泰地区'], ['安庆'], ['安顺'], ['鞍山'], ['克孜勒苏州'], ['安阳'], ['蚌埠'], ['白城'], ['保定'], ['北海'], ['宝鸡'], ['北京'], ['毕节'], ['博州'], ['白山'], ['百色'], ['保山'], ['白沙'], ['包头'], ['保亭'], ['本溪'], ['巴彦淖尔'], ['白银'], ['巴中'], ['滨州'], ['亳州'], ['长春'], ['昌都'], ['常德'], ['成都'], ['承德'], ['赤峰'], ['昌吉州'], ['五家渠'], ['昌江'], ['澄迈'], ['重庆'], ['长沙'], ['常熟'], ['楚雄州'], ['朝阳'], ['沧州'], ['长治'], ['常州'], ['潮州'], ['郴州'], ['池州'], ['崇左'], ['滁州'], ['定安'], ['丹东'], ['东方'], ['东莞'], ['德宏州'], ['大理州'], ['大连'], ['大庆'], ['大同'], ['定西'], ['大兴安岭地区'], ['德阳'], ['东营'], ['黔南州'], ['达州'], ['德州'], ['儋州'], ['鄂尔多斯'], ['恩施州'], ['鄂州'], ['防城港'], ['佛山'], ['抚顺'], ['阜新'], ['阜阳'], ['富阳'], ['抚州'], ['福州'], ['广安'], ['贵港'], ['桂林'], ['果洛州'], ['甘南州'], ['固原'], ['广元'], ['贵阳'], ['甘孜州'], ['赣州'], ['广州'], ['淮安'], ['海北州'], ['鹤壁'], ['淮北'], ['河池'], ['海东地区'], ['邯郸'], ['哈尔滨'], ['合肥'], ['鹤岗'], ['黄冈'], ['黑河'], ['红河州'], ['怀化'], ['呼和浩特'], ['海口'], ['呼伦贝尔'], ['葫芦岛'], ['哈密地区'], ['海门'], ['海南州'], ['淮南'], ['黄南州'], ['衡水'], ['黄山'], ['黄石'], ['和田地区'], ['海西州'], ['河源'], ['衡阳'], ['汉中'], ['杭州'], ['菏泽'], ['贺州'], ['湖州'], ['惠州'], ['吉安'], ['金昌'], ['晋城'], ['景德镇'], ['金华'], ['西双版纳州'], ['九江'], ['吉林'], ['即墨'], ['江门'], ['荆门'], ['佳木斯'], ['济南'], ['济宁'], ['胶南'], ['酒泉'], ['句容'], ['湘西州'], ['金坛'], ['鸡西'], ['嘉兴'], ['江阴'], ['揭阳'], ['济源'], ['嘉峪关'], ['胶州'], ['焦作'], ['锦州'], ['晋中'], ['荆州'], ['库尔勒'], ['开封'], ['黔东南州'], ['克拉玛依'], ['昆明'], ['喀什地区'], ['昆山'], ['临安'], ['六安'], ['来宾'], ['聊城'], ['临沧'], ['娄底'], ['乐东'], ['廊坊'], ['临汾'], ['临高'], ['漯河'], ['丽江'], ['吕梁'], ['陇南'], ['六盘水'], ['拉萨'], ['乐山'], ['丽水'], ['凉山州'], ['陵水'], ['莱芜'], ['莱西'], ['临夏州'], ['溧阳'], ['辽阳'], ['辽源'], ['临沂'], ['龙岩'], ['洛阳'], ['连云港'], ['莱州'], ['兰州'], ['林芝'], ['柳州'], ['泸州'], ['马鞍山'], ['牡丹江'], ['茂名'], ['眉山'], ['绵阳'], ['梅州'], ['宁波'], ['南昌'], ['南充'], ['宁德'], ['内江'], ['南京'], ['怒江州'], ['南宁'], ['南平'], ['那曲地区'], ['南通'], ['南阳'], ['平度'], ['平顶山'], ['普洱'], ['盘锦'], ['蓬莱'], ['平凉'], ['莆田'], ['萍乡'], ['濮阳'], ['攀枝花'], ['青岛'], ['琼海'], ['秦皇岛'], ['曲靖'], ['齐齐哈尔'], ['七台河'], ['黔西南州'], ['清远'], ['庆阳'], ['钦州'], ['衢州'], ['泉州'], ['琼中'], ['荣成'], ['日喀则'], ['乳山'], ['日照'], ['韶关'], ['寿光'], ['上海'], ['绥化'], ['石河子'], ['石家庄'], ['商洛'], ['三明'], ['三门峡'], ['山南'], ['遂宁'], ['四平'], ['商丘'], ['宿迁'], ['上饶'], ['汕头'], ['汕尾'], ['绍兴'], ['三亚'], ['邵阳'], ['沈阳'], ['十堰'], ['*'], ['双鸭山'], ['深圳'], ['朔州'], ['宿州'], ['随州'], ['苏州'], ['石嘴山'], ['泰安'], ['塔城地区'], ['太仓'], ['铜川'], ['屯昌'], ['通化'], ['天津'], ['铁岭'], ['通辽'], ['铜陵'], ['吐鲁番地区'], ['铜仁地区'], ['唐山'], ['天水'], ['太原'], ['台州'], ['泰州'], ['文昌'], ['文登'], ['潍坊'], ['瓦房店'], ['威海'], ['乌海'], ['芜湖'], ['武汉'], ['吴江'], ['乌兰察布'], ['乌鲁木齐'], ['渭南'], ['万宁'], ['文山州'], ['武威'], ['无锡'], ['温州'], ['吴忠'], ['梧州'], ['五指山'], ['西安'], ['兴安盟'], ['许昌'], ['宣城'], ['襄阳'], ['孝感'], ['迪庆州'], ['锡林郭勒盟'], ['厦门'], ['西宁'], ['咸宁'], ['湘潭'], ['邢台'], ['新乡'], ['咸阳'], ['新余'], ['信阳'], ['忻州'], ['徐州'], ['雅安'], ['延安'], ['延边州'], ['宜宾'], ['盐城'], ['宜昌'], ['宜春'], ['银川'], ['运城'], ['伊春'], ['云浮'], ['阳江'], ['营口'], ['榆林'], ['玉林'], ['伊犁哈萨克州'], ['阳泉'], ['玉树州'], ['烟台'], ['鹰潭'], ['义乌'], ['宜兴'], ['玉溪'], ['益阳'], ['岳阳'], ['扬州'], ['永州'], ['淄博'], ['自贡'], ['珠海'], ['湛江'], ['镇江'], ['诸暨'], ['张家港'], ['张家界'], ['张家口'], ['周口'], ['驻马店'], ['章丘'], ['肇庆'], ['中山'], ['舟山'], ['昭通'], ['中卫'], ['张掖'], ['招远'], ['资阳'], ['遵义'], ['枣庄'], ['漳州'], ['郑州'], ['株洲']]
394