使用Python的requests 和BeautifulSoup模块，Python 2.7.12可在命令行中直接使用pip进行模块安装。爬虫的核心是利用BeautifulSoup的select语句获取需要的信息。
pip install requests
pip install bs4以武汉市2017年5~7月的历史为例爬取天气网中武汉市的历史天气数据。
7月对应的网址为http://lishi.tianqi.com/wuhan/201707.html
1.requests模块获取网页内容
url='http://lishi.tianqi.com/wuhan/201707.html'
response = requests.get(url)
soup = BeautifulSoup(response.text, 'html.parser') 2.利用.select语句找到网页中天气数据所在的div
weather_list = soup.select('div[class="tqtongji2"]') 3.找出日期、最高气温、最低气温、天气等数据，用li.string获取li中的信息。
ul_list = weather.select('ul')
for ul in ul_list:
li_list= ul.select('li')
for li in li_list:
li.string.encode('utf-8') #具体的天气信息具体代码实现如下：
#encoding:utf-8
import requests
from bs4 import BeautifulSoup
urls = ["http://lishi.tianqi.com/wuhan/201707.html",
"http://lishi.tianqi.com/wuhan/201706.html",
"http://lishi.tianqi.com/wuhan/201705.html"]
file = open('wuhan_weather.csv','w')
for url in urls:
response = requests.get(url)
soup = BeautifulSoup(response.text, 'html.parser')
weather_list = soup.select('div[class="tqtongji2"]')
for weather in weather_list:
weather_date = weather.select('a')[0].string.encode('utf-8')
ul_list = weather.select('ul')
i=0
for ul in ul_list:
li_list= ul.select('li')
str=""
for li in li_list:
str += li.string.encode('utf-8')+','
if i!=0:
file.write(str+'\n')
i+=1
file.close() 最后的结果：