前言
python爬虫，web spider。爬取网站获取网页数据，并进行分析提取。

基本模块使用的是 urllib，urllib2，re，等模块

（一）基本用法，例子

（1）进行基本GET请求，获取网页html

#!coding=utf-8
import urllib
import urllib2

url = 'http://www.baidu.com/'
# 获取请求
request = urllib2.Request(url)
try:
    # 根据request，得到返回response
    response = urllib2.urlopen(request)
except urllib2.HTTPError, e:
    if hasattr(e, 'reason'):
        print e.reason
# 读取response的body
html = response.read()
# 读取response的headers
headers = response.info()

（2）表单提交

#!coding=utf-8
import urllib2
import urllib

post_url = ''

post_data = urllib.urlencode({
    'username': 'username',
    'password': 'password',
})

post_headers = {
    'User-Agent': 'Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:31.0) Gecko/20100101 Firefox/31.0',
}

request = urllib2.Request(
    url=post_url,
    data=post_data,
    headers=post_headers,
)

response = urllib2.urlopen(request)

html = response.read()

(3)

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#!coding=utf-8

import urllib2
import re

page_num = 1
url = 'http://tieba.baidu.com/p/3238280985?see_lz=1&pn='+str(page_num)
myPage = urllib2.urlopen(url).read().decode('gbk')

myRe = re.compile(r'class="d_post_content j_d_post_content ">(.*?)</div>', re.DOTALL)
items = myRe.findall(myPage)

f = open('baidu.txt', 'a+')

import sys
reload(sys)
sys.setdefaultencoding('utf-8')

i = 0
texts = []
for item in items:
    i += 1
    print i
    text = item.replace('<br>', '')
    text.replace('\n', '').replace(' ', '') + '\n'
    print text
    f.write(text)

f.close()

(4)

#coding:utf-8
'''
    模拟登陆163邮箱并下载邮件内容

'''
import urllib
import urllib2
import cookielib
import re
import time
import json

class Email163:
    header = {'User-Agent':'Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.6) Gecko/20091201 Firefox/3.5.6'}
    user = ''
    cookie = None
    sid = None
    mailBaseUrl='http://twebmail.mail.163.com'

    def __init__(self):
        self.cookie = cookielib.CookieJar()
        cookiePro = urllib2.HTTPCookieProcessor(self.cookie)
        urllib2.install_opener(urllib2.build_opener(cookiePro))

    def login(self,user,pwd):
        '''
            登录
        '''
        postdata = urllib.urlencode({
                'username':user,
                'password':pwd,
                'type':1
            })
        #注意版本不同，登录URL也不同
        req = urllib2.Request(
                url='https://ssl.mail.163.com/entry/coremail/fcg/ntesdoor2?funcid=loginone&language=-1&passtype=1&iframe=1&product=mail163&from=web&df=email163&race=-2_45_-2_hz&module=&uid='+user+'&style=10&net=t&skinid=null',
                data=postdata,
                headers=self.header,
            )
        res = str(urllib2.urlopen(req).read())
        #print res
        patt = re.compile('sid=([^"]+)',re.I)
        patt = patt.search(res)

        uname = user.split('@')[0]
        self.user = user
        if patt:
            self.sid = patt.group(1).strip()
            #print self.sid
            print '%s Login Successful.....'%(uname)
        else:
            print '%s Login failed....'%(uname)


    def getInBox(self):
        '''
            获取邮箱列表
        '''
        print '\nGet mail lists.....\n'
        sid = self.sid
        url = self.mailBaseUrl+'/jy3/list/list.do?sid='+sid+'&fid=1&fr=folder'
        res = urllib2.urlopen(url).read()
        #获取邮件列表
        mailList = []
        patt = re.compile('<div\s+class="tdLike Ibx_Td_From"[^>]+>.*?href="([^"]+)"[^>]+>(.*?)<\/a>.*?<div\s+class="tdLike Ibx_Td_Subject"[^>]+>.*?href="[^>]+>(.*?)<\/a>',re.I|re.S)
        patt = patt.findall(res)
        if patt==None:
            return mailList

        for i in patt:
            line =  {
                    'from':i[1].decode('utf8'),
                     'url':self.mailBaseUrl+i[0],
                     'subject':i[2].decode('utf8')
                     }
            mailList.append(line)

        return mailList


    def getMailMsg(self,url):
        '''
            下载邮件内容
        '''
        content=''
        print '\n Download.....%s\n'%(url)
        res = urllib2.urlopen(url).read()

        patt = re.compile('contentURL:"([^"]+)"',re.I)
        patt = patt.search(res)
        if patt==None:
            return content
        url = '%s%s'%(self.mailBaseUrl,patt.group(1))
        time.sleep(1)
        res = urllib2.urlopen(url).read()
        Djson = json.JSONDecoder(encoding='utf8')
        jsonRes = Djson.decode(res)
        if 'resultVar' in jsonRes:
            content = Djson.decode(res)['resultVar']
        time.sleep(3)
        return content


'''
    Demon
'''
#初始化
mail163 = Email163()
#登录
mail163.login('lpe234@163.com','944898186')
time.sleep(2)

#获取收件箱
elist = mail163.getInBox()

#获取邮件内容
for i in elist:
    print '主题：%s   来自：%s  内容：\n%s'%(i['subject'].encode('utf8'),i['from'].encode('utf8')

（５）需要登陆的情况

#1 cookie的处理
 
import urllib2, cookielib
cookie_support= urllib2.HTTPCookieProcessor(cookielib.CookieJar())
opener = urllib2.build_opener(cookie_support, urllib2.HTTPHandler)
urllib2.install_opener(opener)
content = urllib2.urlopen('http://XXXX').read()
 
#2 用代理和cookie
 
opener = urllib2.build_opener(proxy_support, cookie_support, urllib2.HTTPHandler)
 
#3 表单的处理
 
import urllib
postdata=urllib.urlencode({
    'username':'XXXXX',
    'password':'XXXXX',
    'continueURI':'http://www.verycd.com/',
    'fk':fk,
    'login_submit':'登录'
})
 
req = urllib2.Request(
    url = 'http://secure.verycd.com/signin/*/http://www.verycd.com/',
    data = postdata
)
result = urllib2.urlopen(req).read()
 
#4 伪装成浏览器访问
 
headers = {
    'User-Agent':'Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.6) Gecko/20091201 Firefox/3.5.6'
}
req = urllib2.Request(
    url = 'http://secure.verycd.com/signin/*/http://www.verycd.com/',
    data = postdata,
    headers = headers
)
 
#5 反”反盗链”
 
headers = {
    'Referer':'http://www.cnbeta.com/articles'
}

（６）多线程

from threading import Thread
from Queue import Queue
from time import sleep
#q是任务队列
#NUM是并发线程总数
#JOBS是有多少任务
q = Queue()
NUM = 2
JOBS = 10
#具体的处理函数，负责处理单个任务
def do_somthing_using(arguments):
    print arguments
#这个是工作进程，负责不断从队列取数据并处理
def working():
    while True:
        arguments = q.get()
        do_somthing_using(arguments)
        sleep(1)
        q.task_done()
#fork NUM个线程等待队列
for i in range(NUM):
    t = Thread(target=working)
    t.setDaemon(True)
    t.start()
#把JOBS排入队列
for i in range(JOBS):
    q.put(i)
#等待所有JOBS完成
q.join()