python爬虫的几种数据解析提取方式

使用python爬虫，无论是requests库还是urllib库爬取网页源代码后，想要直接获取其中的信息是比较难的，通常要借助一些第三方库来进行解析并信息提取，目前简单快捷的有bs4库、正则表达式和xpath来完成，下面通过一个实例来解释他们具体的使用方式：

import requests
from bs4 import BeautifulSoup
import json
import re
from lxml import etree
from urllib.parse import quote
header={
    
    
"Cookie": "BIDUPSID=1D3E686AE65F1365106D5F2B6DEDA5C9; PSTM=1584013332; BAIDUID=1D3E686AE65F13650E993E0898A5D1CA:SL=0:NR=10:FG=1; BDORZ=B490B5EBF6F3CD402E515D22BCDA1598; BDUSS=2IxN0pKRmVtR1lLV3JqY2ZUSXpFbmF5Q3htbU5wNTh3TWlTQU83a0J2Zy0xVkZmRVFBQUFBJCQAAAAAAAAAAAEAAACm4ladsfnWrsHox-UAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD5IKl8-SCpfQ; BDUSS_BFESS=2IxN0pKRmVtR1lLV3JqY2ZUSXpFbmF5Q3htbU5wNTh3TWlTQU83a0J2Zy0xVkZmRVFBQUFBJCQAAAAAAAAAAAEAAACm4ladsfnWrsHox-UAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD5IKl8-SCpfQ; Hm_lvt_55b574651fcae74b0a9f1cf9c8d7c93a=1596201563,1596236841,1596616615,1596697867; H_PS_PSSID=32292_1428_32301_32361_32327_31254_32349_32045_32394_32405_32429_32117_26350_32482; Hm_lpvt_55b574651fcae74b0a9f1cf9c8d7c93a=1596698546",
"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.105 Safari/537.36"
}
url="https://baike.baidu.com/item/%E5%B0%8F%E6%98%8E/33553"
print(url)
r=requests.get(url,headers=header)
r.encoding=r.apparent_encoding
#第一种，使用bs4库来完成信息的提取
def get_bs4(r):
    soup = BeautifulSoup(r.content, "html.parser")
    str_one = soup.find("div", {
    
    "class": "para"})
    text = str_one.text
    print(str_one.text)
    with open("D://download//demo_bs4.text", "w") as file:
        file.write(text)

#第二种，使用re库来完成
def get_re(r):
    str_two=re.findall('<meta name="description" content="(.*?)\.\.\."',r.text,re.S)
    print(type(str_two))
    # print(str_two)
    # print(r.text)
    with open("D://download//demo_re.text", "w") as file:
        file.write(str(str_two[0]))
# get_re(r)

#第三种，使用xpath来完成
def get_xpath(r):
    str_one=""
    tree=etree.HTML(r.text)
    str_three=tree.xpath('//div[@class="lemma-summary"]//*[@class="para"]/text()')
    #print(str_three)
    for i in str_three:
            str_one=str_one+str(i)
    print(str_one)
#get_xpath(r)