python_赵梦冰_20210128

9：00——20：00
课堂笔记

import requests

from lxml import etree

#将爬虫伪装成浏览器

headers = {'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36'}

#使用get方法发出请求，然后接收响应

r = requests.get('https://www.baidu.com',headers=headers)

# r = requests.get('https://www.douban.com',headers=headers)

#设置编码集

r.encoding = 'uft-8'

#输出网页内容

# print(r.text)

#将字符串格式的网页转变为etree格式

selector = etree.HTML(r.text)

#获取图片地址

href = selector.xpath('//*[@id="s_lg_img"]/@src')[0]

print(href)

#下载图片

response = requests.get('https:'+href)

# print(response.content)

#保存图片

with open('result.png',mode='wb')as picture:

    picture.write(response.content)

import requests

from lxml import etree

# response = requests.get(r'D:\workspace\python\day10\sample.html')

# response.encoding = 'utf-8'

# print(response.text)

with open('D:\workspace\python\day10\sample.html','r')as file:

    page = file.read()

selector = etree.HTML(page)

ul = selector.xpath('//div/ul')

print(ul)

#获取所有的li元素

# lis = selector.xpath('//div/ul/li')

#获取第二个li

# li2 = selector.xpath('//div/ul/li')[1]

#或

#多个同名元素编号从1开始

li2 = selector.xpath('//div/ul/li[2]')

print(li2)

#精确定位

li3 = selector.xpath('//div/ul/li[@class="item-inactive"]')

print(li3)

ass = selector.xpath('//div/ul/li/a')

print(ass)

#绝对路径

a4 = selector.xpath('//div/ul/li/a[@href="link4.html"]')

print(a4)

#通过文本来定位元素   相对路径

a4 = selector.xpath('//*[text()="fourth item"]')

print(a4)