How to implement web crawler in python

How to implement a web crawler in python: 1. Use the get method in the request library to request the web page content of the url; 2. The [find()] and [find_all()] methods can traverse the html file and extract Specify information.

How to implement a web crawler in python:

The first step: crawling

Use the get method in the request library to request the web page content of the url

Write code

[root@localhost demo]# touch demo.py
[root@localhost demo]# vim demo.py

#web爬虫学习 -- 分析
#获取页面信息
 
#输入：url
#处理：request库函数获取页面信息，并将网页内容转换成为人能看懂的编码格式
#输出：爬取到的内容
 
import requests
 
def getHTMLText(url):
    try:
        r = requests.get( url, timeout=30 )
        r.raise_for_status()    #如果状态码不是200，产生异常
        r.encoding = 'utf-8'    #字符编码格式改成 utf-8
        return r.text
    except:
        #异常处理
        return " error "
 
url = "http://www.baidu.com"
print( getHTMLText(url) )

[root@localhost demo]# python3 demo.py

Step 2: Analysis

Use the BeautifulSoup class in the bs4 library to generate an object. The find() and find_all() methods can traverse this html file and extract specified information.

Writing code

[root@localhost demo]# touch demo1.py
[root@localhost demo]# vim demo1.py
#web爬虫学习 -- 分析
#获取页面信息
 
#输入：url
#处理：request库获取页面信息，并从爬取到的内容中提取关键信息
#输出：打印输出提取到的关键信息
 
import requests
from bs4 import BeautifulSoup
import re
 
def getHTMLText(url):
    try:
        r = requests.get( url, timeout=30 )
        r.raise_for_status()    #如果状态码不是200，产生异常
        r.encoding = 'utf-8'    #字符编码格式改成 utf-8
        return r.text
    except:
        #异常处理
        return " error "
 
def findHTMLText(text):
    soup = BeautifulSoup( text, "html.parser" )    #返回BeautifulSoup对象
    return soup.find_all(string=re.compile( '百度' )) #结合正则表达式，实现字符串片段匹配
 
url = "http://www.baidu.com"
text = getHTMLText(url)        #获取html文本内容
res = findHTMLText(text)    #匹配结果
 
print(res)        #打印输出

[root@localhost demo]# python3 demo1.py

##Related free learning recommendations: python video tutorial

The above is the detailed content of How to implement web crawler in python. For more information, please follow other related articles on the PHP Chinese website!