#Python进阶(二十)-Python爬虫实例讲解

本篇博文主要讲解Python爬虫实例，重点包括爬虫技术架构，组成爬虫的关键模块：URL管理器、HTML下载器和HTML解析器。

##爬虫简单架构

 ##程序入口函数(爬虫调度段)

#coding:utf8

import time, datetime

from maya_Spider import url_manager, html_downloader, html_parser, html_outputer

class Spider_Main(object): #初始化操作 def __init__(self): #设置url管理器 self.urls = url_manager.UrlManager() #设置HTML下载器 self.downloader = html_downloader.HtmlDownloader() #设置HTML解析器 self.parser = html_parser.HtmlParser() #设置HTML输出器 self.outputer = html_outputer.HtmlOutputer() #爬虫调度程序 def craw(self, root_url): count = 1 self.urls.add_new_url(root_url) while self.urls.has_new_url(): try: new_url = self.urls.get_new_url() print('craw %d : %s' % (count, new_url)) html_content = self.downloader.download(new_url) new_urls, new_data = self.parser.parse(new_url, html_content) self.urls.add_new_urls(new_urls) self.outputer.collect_data(new_data) if count == 10: break count = count + 1 except: print('craw failed') self.outputer.output_html()

if __name__ == '__main__': #设置爬虫入口 root_url = 'http://baike.baidu.com/view/21087.htm' #开始时间 print('开始计时..............') start_time = datetime.datetime.now() obj_spider = Spider_Main() obj_spider.craw(root_url) #结束时间 end_time = datetime.datetime.now() print('总用时：%ds'% (end_time - start_time).seconds)1

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##URL管理器

class UrlManager(object): def __init__(self): self.new_urls = set() self.old_urls = set() def add_new_url(self, url): if url is None: return if url not in self.new_urls and url not in self.old_urls: self.new_urls.add(url) def add_new_urls(self, urls): if urls is None or len(urls) == 0: return for url in urls: self.add_new_url(url) def has_new_url(self): return len(self.new_urls) != 0 def get_new_url(self): new_url = self.new_urls.pop() self.old_urls.add(new_url) return new_url1

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##网页下载器

import urllib

import urllib.request

class HtmlDownloader(object): def download(self, url): if url is None: return None #伪装成浏览器访问，直接访问的话csdn会拒绝 user_agent = 'Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)' headers = {'User-Agent':user_agent} #构造请求 req = urllib.request.Request(url,headers=headers) #访问页面 response = urllib.request.urlopen(req) #python3中urllib.read返回的是bytes对象，不是string,得把它转换成string对象，用bytes.decode方法 return response.read().decode()1

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##网页解析器

import re

import urllib

from urllib.parse import urlparse

from bs4 import BeautifulSoup

class HtmlParser(object): def _get_new_urls(self, page_url, soup): new_urls = set() #/view/123.htm links = soup.find_all('a', href=re.compile(r'/item/.*?')) for link in links: new_url = link['href'] new_full_url = urllib.parse.urljoin(page_url, new_url) new_urls.add(new_full_url) return new_urls #获取标题、摘要 def _get_new_data(self, page_url, soup): #新建字典 res_data = {} #url res_data['url'] = page_url #

Python

获得标题标签 title_node = soup.find('dd', class_="lemmaWgt-lemmaTitle-title").find('h1') print(str(title_node.get_text())) res_data['title'] = str(title_node.get_text()) #