python爬虫之定位网页元素的三种方式

import requests
 from bs4 import BeautifulSoup
 from lxml import etree
 
 # 通过find定位标签
 # BeautifulSoup文档：https://www.crummy.com/software/BeautifulSoup/bs4/doc/index.zh.html
 def bs_parse_movies(html):
     movie_list = []
     soup = BeautifulSoup(html, "lxml")
     # 查找所有class属性为hd的div标签
     div_list = soup.find_all('div', class_='hd')
     # 获取每个div中的a中的span（第一个），并获取其文本
     for each in div_list:
         movie = each.a.span.text.strip()
         movie_list.append(movie)
 
     return movie_list
 
 # css选择器定位标签
 # 更多ccs选择器语法：http://www.w3school.com.cn/cssref/css_selectors.asp
 # 注意：BeautifulSoup并不是每个语法都支持
 def bs_css_parse_movies(html):
     movie_list = []
     soup = BeautifulSoup(html, "lxml")
     # 查找所有class属性为hd的div标签下的a标签的第一个span标签
     div_list = soup.select('div.hd > a > span:nth-of-type(1)')
     # 获取每个span的文本
     for each in div_list:
         movie = each.text.strip()
         movie_list.append(movie)
 
     return movie_list
 
 # XPATH定位标签
 # 更多xpath语法：https://blog.csdn.net/gongbing798930123/article/details/78955597
 def xpath_parse_movies(html):
     et_html = etree.HTML(html)
     # 查找所有class属性为hd的div标签下的a标签的第一个span标签
     urls = et_html.xpath("//div[@class='hd']/a/span[1]")
 
     movie_list = []
     # 获取每个span的文本
     for each in urls:
         movie = each.text.strip()
         movie_list.append(movie)
 
     return movie_list
 
 def get_movies():
     headers = {
         'user-agent': 'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.82 Safari/537.36',
         'Host': 'movie.douban.com'
     }
 
     link = 'https://movie.douban.com/top250'
     r = requests.get(link, headers=headers, timeout=10)
     print("响应状态码:", r.status_code)
     if 200 != r.status_code:
         return None
 
     # 三种定位元素的方式：
 
     # 普通BeautifulSoup find
     return bs_parse_movies(r.text)
     # BeautifulSoup css select
     return bs_css_parse_movies(r.text)
     # xpath
     return xpath_parse_movies(r.text)
 
 movies = get_movies()
 print(movies)