python增量爬虫pyspider

1.为了能够将爬取到的数据存入本地数据库，现在本地创建一个MySQL数据库example，然后 
在数据库中建立一张表格test，示例如下：

DROP TABLE IF EXISTS `test`;
CREATE TABLE `douban_db` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `url` varchar(20) NOT NULL,
  `direct`  varchar(30),
  `performer`  date,
  `type`  varchar(30),
  `district` varchar(20) NOT NULL,
  `language`  varchar(30),
  `date`  varchar(30),
  `time`  varchar(30),
  `alias` varchar(20) NOT NULL,
  `score`  varchar(30),
  `comments`  varchar(300),
  `scenario`  varchar(300),
  `IMDb`  varchar(30),
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8;

2.如果使用开源框架pyspider来进行爬虫的话，默认情况下，会把爬取到的结果存放到result.db这个sqilite数据库中，但是为了方便操作，我们将结果存放到mysql中。接下 
来要做的一个操作就是重写on_result方法，实例化调用我们自己实现的SQL方法，具体 
实例如下：

#!/usr/bin/env python
# -*- encoding: utf-8 -*-
# Created on 2015-03-20 09:46:20
# Project: fly_spider

import re
from pyspider.database.mysql.mysqldb import SQL
from pyspider.libs.base_handler import *


class Handler(BaseHandler):

    headers= {
                          "Accept":"text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
    "Accept-Encoding":"gzip, deflate, sdch",
    "Accept-Language":"zh-CN,zh;q=0.8",
    "Cache-Control":"max-age=0",
    "Connection":"keep-alive",
    "User-Agent":"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.101 Safari/537.36"
    }

    crawl_config = {
        "headers" : headers,
        "timeout" : 100
    }
    @every(minutes=24 * 60)
    def on_start(self):
        self.crawl('http://movie.douban.com/tag/', callback=self.index_page)

    @config(age=10 * 24 * 60 * 60)
    def index_page(self, response):
        for each in response.doc('a[href^="http"]').items():
            if re.match("http://movie.douban.com/tag/w+", each.attr.href, re.U):
                self.crawl(each.attr.href, callback=self.list_page)  
    @config(age=10*24*60*60, priority=2)                
    def list_page(self, response):
        for each in response.doc('html > body > div#wrapper > div#content > div.grid-16-8.clearfix > div.article > div > table tr.item > td > div.pl2 > a').items():
            self.crawl(each.attr.href, priority=9, callback=self.detail_page)  

    @config(priority=3)
    def detail_page(self, response):
        return {
            "url": response.url,
            "title": response.doc('html > body > #wrapper > #content > h1 > span').text(),
            "direct": ",".join(x.text() for x in response.doc('a[rel="v:directedBy"]').items()),
            "performer": ",".join(x.text() for x in response.doc('a[rel="v:starring"]').items()),
            "type": ",".join(x.text() for x in response.doc('span[property="v:genre"]').items()),
#            "district":  "".join(x.text() for x in response.doc('a[rel="v:starring"]').items()),
#            "language":  "".join(x.text() for x in response.doc('a[rel="v:starring"]').items()),
            "date":  ",".join(x.text() for x in response.doc('span[property="v:initialReleaseDate"]').items()),
            "time":  ",".join(x.text() for x in response.doc('span[property="v:runtime"]').items()),
#            "alias":  "".join(x.text() for x in response.doc('a[rel="v:starring"]').items()),
            "score": response.doc('.rating_num').text(),
            "comments": response.doc('html > body > div#wrapper > div#content > div.grid-16-8.clearfix > div.article > div#comments-section > div.mod-hd > h2 > i').text(),
            "scenario": response.doc('html > body > div#wrapper > div#content > div.grid-16-8.clearfix > div.article > div.related-info > div#link-report.indent').text(),
            "IMDb":  "".join(x.text() for x in response.doc('span[href]').items()),
            }

    def on_result(self, result):
        if not result or not result['title']:
            return
        sql = SQL()
        sql.replace('douban_db',**result)    

关于上面这段代码，有下面几点需要说明的： 
a. 为了避免服务器判断出客户端在进行爬虫操作，从而禁止ip访问（具体表现为出现403禁止访问），我们需要在发出请求的时候加上一个http头，伪装成使用浏览器访问，具体用法如下：

    headers= {
                          "Accept":"text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
    "Accept-Encoding":"gzip, deflate, sdch",
    "Accept-Language":"zh-CN,zh;q=0.8",
    "Cache-Control":"max-age=0",
    "Connection":"keep-alive",
    "User-Agent":"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.101 Safari/537.36"
    }

    crawl_config = {
        "headers" : headers,
        "timeout" : 100
    }

b. @every(minutes=24 * 60)表示每天执行一次 
@config(age=10 * 24 * 60 * 60)表示数据10天后就过期了

c. 接下来是一个比较重要的地方，重写on_result方法，相当于实现了一个多态，程序在最后返回时，会执行on_result方法，默认的情况下，on_result是将数据刷入sqlite中，但是如果我们需要将数据插入mysql中，就需要重写on_result方法，具体使用如下：

    def on_result(self, result):
        if not result or not result['title']:
            return
        sql = SQL()
        sql.replace('test',**result)    

注意这里的if not result or not result[‘title’]:这句判断很重要，不然的会会报错，提示result是未定义类型的。

3.在上面的额代码中，提到了实例化调用我们自己实现的SQL方法，并且引用了from pyspider.database.mysql.mysqldb import SQL这个库文件，那么就必须在这个目录下实现这个库，具体如下： 
把下面内容文文放到pyspider/pyspider/database/mysql/目录下命名为mysqldb.py

from six import itervalues
import mysql.connector
from datetime import date, datetime, timedelta

class SQL:

        username = 'root'  #数据库用户名
        password = 'root'  #数据库密码
        database = 'test'  #数据库
        host = '172.30.25.231'  #数据库主机地址
        connection = ''
        connect = True
    placeholder = '%s'

        def __init__(self):
                if self.connect:
                        SQL.connect(self)
    def escape(self,string):
        return '`%s`' % string
        def connect(self):
            config = {
                'user':SQL.username,
                'password':SQL.password,
                'host':SQL.host
            }
            if SQL.database != None:
                config['database'] = SQL.database

            try:
                cnx = mysql.connector.connect(**config)
                SQL.connection = cnx
                return True
            except mysql.connector.Error as err:

            if (err.errno == errorcode.ER_ACCESS_DENIED_ERROR):
                print "The credentials you provided are not correct."
            elif (err.errno == errorcode.ER_BAD_DB_ERROR):
                print "The database you provided does not exist."
            else:
                print "Something went wrong: " , err
            return False


    def replace(self,tablename=None,**values):
        if SQL.connection == '':
                    print "Please connect first"
                    return False

                tablename = self.escape(tablename )
                if values:
                        _keys = ", ".join(self.escape(k) for k in values)
                        _values = ", ".join([self.placeholder, ] * len(values))
                        sql_query = "REPLACE INTO %s (%s) VALUES (%s)" % (tablename, _keys, _values)
                else:
                        sql_query = "REPLACE INTO %s DEFAULT VALUES" % tablename


        cur = SQL.connection.cursor()
                try:
                    if values:
                            cur.execute(sql_query, list(itervalues(values)))
                    else:
                            cur.execute(sql_query)
                    SQL.connection.commit()
                    return True
                except mysql.connector.Error as err:
                    print ("An error occured: {}".format(err))
                    return False

学习文档：http://blog.binux.me/2015/01/pyspider-tutorial-level-1-html-and-css-selector/ 
测试环境：http://demo.pyspider.org/