http://cuiqingcai.com/1972.html
本文重在分析理解作者代码所用函数，以及相关思路。以作对于python爬虫稍微深入一些的扩展的加深理解。
废话少数，上代码——
作者分为四个文件。
(tool.py)
#-*- coding:utf-8 -*-
import re
#处理页面标签类
class Tool:
#将超链接广告剔除
removeADLink = re.compile('<div class="link_layer.*?</div>')
#去除img标签,1-7位空格,
removeImg = re.compile('<img.*?>| {1,7}| ')
#删除超链接标签
removeAddr = re.compile('<a.*?>|</a>')
#把换行的标签换为\n
replaceLine = re.compile('<tr>|<div>|</div>|</p>')
#将表格制表<td>替换为\t
replaceTD= re.compile('<td>')
#将换行符或双换行符替换为\n
replaceBR = re.compile('<br><br>|<br>')
#将其余标签剔除
removeExtraTag = re.compile('<.*?>')
#将多行空行删除
removeNoneLine = re.compile('\n+')
def replace(self,x):
x = re.sub(self.removeADLink,"",x)
x = re.sub(self.removeImg,"",x)
x = re.sub(self.removeAddr,"",x)
x = re.sub(self.replaceLine,"\n",x)
x = re.sub(self.replaceTD,"\t",x)
x = re.sub(self.replaceBR,"\n",x)
x = re.sub(self.removeExtraTag,"",x)
x = re.sub(self.removeNoneLine,"\n",x)
#strip()将前后多余内容删除
return x.strip()
——该文件起到一个处理文本内容的作用，分别利用html页面中的各种标签进行替换，最后用类打包
(spider.py)
# -*- coding:utf-8 -*-
import urllib2
import re
import time
import types
import sys
from bs4 import BeautifulSoup
#引用文件
import page
import mysql
class Spider:
#初始化
def __init__(self):
self.page_num = 1
self.total_num = None
self.page_spider = page.Page()
self.mysql = mysql.Mysql()
#获取当前时间
def getCurrentTime(self):
return time.strftime('[%Y-%m-%d %H:%M:%S]',time.localtime(time.time()))
#获取当前时间
def getCurrentDate(self):
return time.strftime('%Y-%m-%d',time.localtime(time.time()))
#通过网页的页码数来构建网页的URL
def getPageURLByNum(self, page_num):
page_url = "http://iask.sina.com.cn/c/978-all-" + str(page_num) + ".html" #str()只是返回一个对象的字符串形式，原对象并未改变
return page_url
#通过传入网页页码来获取网页的HTML
def getPageByNum(self, page_num):
request = urllib2.Request(self.getPageURLByNum(page_num))
try:
response = urllib2.urlopen(request)
except urllib2.URLError, e:
if hasattr(e, "code"):
print self.getCurrentTime(),"获取页面失败,错误代号", e.code
return None
if hasattr(e, "reason"):
print self.getCurrentTime(),"获取页面失败,原因", e.reason
return None
else:
page = response.read().decode("utf-8") #网站源码是utf-8格式如此一来传过去的就是一堆字符了
return page
#获取所有的页码数
def getTotalPageNum(self):
print self.getCurrentTime(),"正在获取目录页面个数,请稍候"
page = self.getPageByNum(1)
#匹配所有的页码数,\u4e0b\u4e00\u9875是下一页的UTF8编码
pattern = re.compile(u'<span class="more".*?>.*?<span.*?<a href.*?class="">(.*?)</a>\s*<a.*?\u4e0b\u4e00\u9875</a>', re.S)
match = re.search(pattern, page)
if match:
return match.group(1)
else:
print self.getCurrentTime(),"获取总页码失败"
#分析问题的代码,得到问题的提问者,问题内容,回答个数,提问时间
def getQuestionInfo(self, question):
if not type(question) is types.StringType:
question = str(question)
#print question
pattern = re.compile(u'<span.*?question-face.*?>.*?<img.*?alt="(.*?)".*?</span>.*?<a href="(.*?)".*?>(.*?)</a>.*?answer_num.*?>(\d*).*?</span>.*?answer_time.*?>(.*?)</span>', re.S)
match = re.search(pattern, question)
if match:
#获得提问者
author = match.group(1)
#问题链接
href = match.group(2)
#问题详情
text = match.group(3)
#回答个数
ans_num = match.group(4)
#回答时间
time = match.group(5)
time_pattern = re.compile('\d{4}\-\d{2}\-\d{2}', re.S)
time_match = re.search(time_pattern, time)
if not time_match:
time = self.getCurrentDate()
return [author, href, text, ans_num, time]
else:
return None
#获取全部问题
def getQuestions(self, page_num):
#获得目录页面的HTML
page = self.getPageByNum(page_num)
soup = BeautifulSoup(page)
#分析获得所有问题
questions = soup.select("div.question_list ul li")
#遍历每一个问题
for question in questions:
#获得问题的详情
info = self.getQuestionInfo(question)
if info:
#得到问题的URL
url = "http://iask.sina.com.cn/" + info[1]
#通过URL来获取问题的最佳答案和其他答案
ans = self.page_spider.getAnswer(url)
print self.getCurrentTime(),"当前爬取第",page_num,"的内容,发现一个问题",info[2],"回答数量",info[3]
#构造问题的字典,插入问题
ques_dict = {
"text": info[2],
"questioner": info[0],
"date": info[4],
"ans_num": info[3],
"url": url
}
#获得插入的问题的自增ID
insert_id = self.mysql.insertData("iask_questions",ques_dict)
#得到最佳答案
good_ans = ans[0]
print self.getCurrentTime(),"保存到数据库,此问题的ID为",insert_id
#如果存在最佳答案,那么就插入
if good_ans:
print self.getCurrentTime(),insert_id,"号问题存在最佳答案",good_ans[0]
#构造最佳答案的字典
good_ans_dict = {
"text": good_ans[0],
"answerer": good_ans[1],
"date": good_ans[2],
"is_good": str(good_ans[3]),
"question_id": str(insert_id)
}
#插入最佳答案
if self.mysql.insertData("iask_answers",good_ans_dict):
print self.getCurrentTime(),"保存最佳答案成功"
else:
print self.getCurrentTime(),"保存最佳答案失败"
#获得其他答案
other_anses = ans[1]
#遍历每一个其他答案
for other_ans in other_anses:
#如果答案存在
if other_ans:
print self.getCurrentTime(),insert_id,"号问题存在其他答案",other_ans[0]
#构造其他答案的字典
other_ans_dict = {
"text": other_ans[0],
"answerer": other_ans[1],
"date": other_ans[2],
"is_good": str(other_ans[3]),
"question_id": str(insert_id)
}
#插入这个答案
if self.mysql.insertData("iask_answers",other_ans_dict):
print self.getCurrentTime(),"保存其他答案成功"
else:
print self.getCurrentTime(),"保存其他答案失败"
#主函数
def main(self):
f_handler=open('out.log', 'w')
sys.stdout=f_handler
page = open('page.txt', 'r')
content = page.readline()
start_page = int(content.strip()) - 1
page.close()
print self.getCurrentTime(),"开始页码",start_page
print self.getCurrentTime(),"爬虫正在启动,开始爬取爱问知识人问题"
self.total_num = self.getTotalPageNum()
print self.getCurrentTime(),"获取到目录页面个数",self.total_num,"个"
if not start_page:
start_page = self.total_num
for x in range(1,start_page):
print self.getCurrentTime(),"正在抓取第",start_page-x+1,"个页面"
try:
self.getQuestions(start_page-x+1)
except urllib2.URLError, e:
if hasattr(e, "reason"):
print self.getCurrentTime(),"某总页面内抓取或提取失败,错误原因", e.reason
except Exception,e:
print self.getCurrentTime(),"某总页面内抓取或提取失败,错误原因:",e
if start_page-x+1 < start_page:
f=open('page.txt','w')
f.write(str(start_page-x+1))
print self.getCurrentTime(),"写入新页码",start_page-x+1
f.close()
spider = Spider()
spider.main()
(page.py)
# -*- coding:utf-8 -*-
import urllib
import urllib2
import re
import time
import types
import tool
from bs4 import BeautifulSoup
#抓取分析某一问题和答案
class Page:
def __init__(self):
self.tool = tool.Tool()
#获取当前时间
def getCurrentDate(self):
return time.strftime('%Y-%m-%d',time.localtime(time.time()))
#获取当前时间
def getCurrentTime(self):
return time.strftime('[%Y-%m-%d %H:%M:%S]',time.localtime(time.time()))
#通过页面的URL来获取页面的代码
def getPageByURL(self, url):
try:
request = urllib2.Request(url)
response = urllib2.urlopen(request)
return response.read().decode("utf-8")
except urllib2.URLError, e:
if hasattr(e, "code"):
print self.getCurrentTime(),"获取问题页面失败,错误代号", e.code
return None
if hasattr(e, "reason"):
print self.getCurrentTime(),"获取问题页面失败,原因", e.reason
return None
#传入一个List,返回它的标签里的内容,如果为空返回None
def getText(self, html):
if not type(html) is types.StringType:
html = str(html)
#提取出<pre>标签里的内容
pattern = re.compile('<pre.*?>(.*?)</pre>', re.S)
match = re.search(pattern, html)
#如果匹配成功
if match:
return match.group(1)
else:
return None
#传入最佳答案的HTML,分析出回答者和回答时间
def getGoodAnswerInfo(self, html):
pattern = re.compile('"answer_tip.*?<a.*?>(.*?)</a>.*?<span class="time.*?>.*?\|(.*?)</span>', re.S)
match = re.search(pattern, html)
#如果匹配,返回回答者和回答时间
if match:
time = match.group(2)
time_pattern = re.compile('\d{2}\-\d{2}\-\d{2}', re.S)
time_match = re.search(time_pattern, time)
if not time_match:
time = self.getCurrentDate()
else:
time = "20"+time
return [match.group(1),time]
else:
return [None,None]
#获得最佳答案
def getGoodAnswer(self, page):
soup = BeautifulSoup(page)
text = soup.select("div.good_point div.answer_text pre")
if len(text) > 0:
#获得最佳答案的内容
ansText = self.getText(str(text[0]))
ansText = self.tool.replace(ansText)
#获得最佳答案的回答者信息
info = soup.select("div.good_point div.answer_tip")
ansInfo = self.getGoodAnswerInfo(str(info[0]))
#将三者组合成一个List
answer = [ansText, ansInfo[0], ansInfo[1],1]
return answer
else:
#如果不存在最佳答案,那么就返回空
return None
#传入回答者HTML,分析出回答者,回答时间
def getOtherAnswerInfo(self, html):
if not type(html) is types.StringType:
html = str(html)
pattern = re.compile('"author_name.*?>(.*?)</a>.*?answer_t">(.*?)</span>', re.S)
match = re.search(pattern, html)
#获得每一个回答的回答者信息和回答时间
if match:
time = match.group(2)
time_pattern = re.compile('\d{2}\-\d{2}\-\d{2}', re.S)
time_match = re.search(time_pattern, time)
if not time_match:
time = self.getCurrentDate()
else:
time = "20"+time
return [match.group(1),time]
else:
return [None,None]
#获得其他答案
def getOtherAnswers(self, page):
soup = BeautifulSoup(page)
results = soup.select("div.question_box li.clearfix .answer_info")
#所有答案,包含好多个List,每个List包含了回答内容,回答者,回答时间
answers = []
for result in results:
#获得回答内容
ansSoup = BeautifulSoup(str(result))
text = ansSoup.select(".answer_txt span pre")
ansText = self.getText(str(text[0]))
ansText = self.tool.replace(ansText)
#获得回答者和回答时间
info = ansSoup.select(".answer_tj")
ansInfo = self.getOtherAnswerInfo(info[0])
#将三者组合成一个List
answer = [ansText, ansInfo[0], ansInfo[1],0]
#加入到answers
answers.append(answer)
return answers
#主函数
def getAnswer(self, url):
if not url:
url = "http://iask.sina.com.cn/b/gQiuSNCMV.html"
page = self.getPageByURL(url)
good_ans = self.getGoodAnswer(page)
other_ans = self.getOtherAnswers(page)
return [good_ans,other_ans]
page = Page()
page.getAnswer(None)
# -*- coding:utf-8 -*-
import MySQLdb
import time
class Mysql:
#获取当前时间
def getCurrentTime(self):
return time.strftime('[%Y-%m-%d %H:%M:%S]',time.localtime(time.time()))
#数据库初始化
def __init__(self):
try:
self.db = MySQLdb.connect('ip','username','password','db_name')
self.cur = self.db.cursor()
except MySQLdb.Error,e:
print self.getCurrentTime(),"连接数据库错误，原因%d: %s" % (e.args[0], e.args[1])
#插入数据
def insertData(self, table, my_dict):
try:
self.db.set_character_set('utf8')
cols = ', '.join(my_dict.keys())
values = '"," '.join(my_dict.values())
sql = "INSERT INTO %s (%s) VALUES (%s)" % (table, cols, '"'+values+'"')
try:
result = self.cur.execute(sql)
insert_id = self.db.insert_id()
self.db.commit()
#判断是否执行成功
if result:
return insert_id
else:
return 0
except MySQLdb.Error,e:
#发生错误时回滚
self.db.rollback()
#主键唯一，无法插入
if "key 'PRIMARY'" in e.args[1]:
print self.getCurrentTime(),"数据已存在，未插入数据"
else:
print self.getCurrentTime(),"插入数据失败，原因 %d: %s" % (e.args[0], e.args[1])
except MySQLdb.Error,e:
print self.getCurrentTime(),"数据库错误，原因%d: %s" % (e.args[0], e.args[1])
