# url管理器
class UrlManager():
def __init__(self):
self.new_urls = set() #未爬取集合
self.old_urls = set() # 已爬取集合
def has_new_url(self):
'''
判断是否有未爬取的URL
:return:
'''
return self.new_url_size() !=0
def get_new_url(self):
'''
获取一个未爬取的URL
:return:
'''
new_url = self.new_urls.pop()
self.old_urls.add(new_url)
return new_url
def add_new_url(self,url):
'''
将新的URL添加到未爬取的集合中
:param url: 单个URL
:return:
'''
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):
'''
将新的URL添加到未爬取的URL集合中
:param urls: URL集合
:return:
'''
if urls is None or len(urls)==0:
return
for url in urls:
self.add_new_url(url)
def new_url_size(self):
'''
获取未爬取URL集合的大小
:return:
'''
return len(self.new_urls)
def old_url_size(self):
'''
获取已经爬取的URL集合的大小
:return:
'''
return len(self.old_urls)
# HTML下载器
import requests
class HtmlDownloader():
def download(self,url):
if url is None:
return None
headers = {'User-Agent': 'Mozilla/5.0 (Macintosh; Intel …) Gecko/20100101 Firefox/57.0'.encode('utf-8')}
r = requests.get(url,headers=headers)
if r.status_code ==200:
r.encoding = 'utf-8'
return r.text
return None
# HTML解析器
import re
from urllib import parse
from bs4 import BeautifulSoup
class HtmlParser():
def parser(self,page_url,html_cont):
'''
用于解析网页内容，抽取URL和数据
:param page_url: 下载页面的URL
:param html_cont: 下载的网页内容
:return:
'''
if page_url is None or html_cont is None:
return
soup = BeautifulSoup(html_cont,'html.parser')
new_urls = self._get_new_urls(page_url,soup)
new_data = self._get_new_data(page_url,soup)
return new_urls,new_data
def _get_new_urls(self,page_url,soup):
'''
抽取新的URL集合
:param page_url: 下载页面的URL
:param soup: soup
:return:
'''
new_urls = set()
#抽取符合要求的a标签
links = soup.find_all('a',href = re.compile(r'/item/.'))
for link in links:
# 提取href属性
new_url = link['href']
# 拼接成完整的网址
new_full_url = parse.urljoin(page_url,new_url)
new_urls.add(new_full_url)
return new_urls
def _get_new_data(self,page_url,soup):
'''
抽取有效数据
:param page_url: 下载页面URL
:param soup:
:return: 返回有效数据
'''
data = {}
data['url'] = page_url
title = soup.find('dd',class_ = 'lemmaWgt-lemmaTitle-title').find('h1')
data['title'] = title.text
summary = soup.find('div',class_ = 'lemma-summary')
#获取tag中包含的所有文本内容
data['summary'] = summary.text
return data
# 数据存储器
import codecs
class DataOutput():
def __init__(self):
self.datas=[]
def store_data(self,data):
if data is None:
return
self.datas.append(data)
def output_html(self):
fout = codecs.open('baike.html','w',encoding='utf-8')
fout.write('<html>')
fout.write('<table>')
fout.write('<table>')
for data in self.datas:
fout.write('<tr>')
fout.write('<td>%s</td>'% data['url'])
fout.write('<td>%s</td>' % data['title'])
fout.write('<td>%s</td>' % data['summary'])
fout.write('</tr>')
self.datas.remove(data)
fout.write('</table>')
fout.write('</table>')
fout.write('</html>')
fout.close()
# 爬虫调度器
class SpiderMan():
def __init__(self):
self.manager = UrlManager()
self.downloader = HtmlDownloader()
self.parser = HtmlParser()
self.output = DataOutput()
def crawl(self,root_url):
#添加入口URL
self.manager.add_new_url(root_url)
# 判断URL管理器中是否有新的URL，同时判断抓取了多少个URL
while (self.manager.has_new_url() and self.manager.old_url_size()<100):
try:
# 从URL管理器获取新的URL
new_url = self.manager.get_new_url()
# HTML下载器下载网页
html = self.downloader.download(new_url)
new_urls,data = self.parser.parser(new_url,html)
# 将抽取的URL添加到URL管理器中
self.manager.add_new_urls(new_urls)
# 数据存储器存储文件
self.output.store_data(data)
print('已经抓取了%s个链接'% self.manager.old_url_size())
except Exception as e:
print('crawl failed %s'% e)
self.output.output_html()
if __name__ =='__main__':
spider_man = SpiderMan()
spider_man.crawl('http://baike.baidu.com/view/284853.htm')
