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Python3下基于bs4和sqlalchemy的爬虫实现

勿忘初心2018-09-29 10:56

本文来自网易云社区

作者:王贝


小学生现在都在学python了,作为专业程序员当然不能落下了,所以,快马加鞭,周六周末在家学起了python3,python3的基本语法比较简单,相比于Java开发更加敏捷,python3的基础就不讲了,这里主要讲下我这里的爬虫小程序的实现逻辑吧

上下模块图:


一目了然,总体上就是这5步,涉及到python3的requests,bs4,re,sqlalchemy这四个模块。
(1)requests:
是一个很强大的http客户端库,提供了丰富的api,比如发一个get请求:
with requests.get(url,params={},headers={}) as rsp:
   res.text   #返回值文本内容
发一个入参为json的post请求:
with requests.post(url,json={},headers={}) as rsp:
   res.text #返回值文本内容
等等。
这里值得说一下,为什么用with as,with会先执行__enter__()方法,其返回值就是as,requests里返回值就是rsp,当with as 这一逻辑行执行结束时,就会执行__exit__()方法,requests里__exit__()方法将request close掉了,这就是程序没有显示调用close的原因。下面程序里会有一个例子彰显with as的功能。
requests还有很多强大的功能,参考:https://www.cnblogs.com/lilinwei340/p/6417689.html。
(2)bs4 BeatifulSoup
学过java的都知道java有个jsoup,jsoup就是对html模版进行解析,变成各个标签集合,这里bs4和jsoup如出一辙,api也基本一致,比如,一下html代码,我们想获取新闻,地图,视频,贴吧 这些内容,只要:
soup=BeautifulSoup(html,'html.parser')
atags=soup.find('div',{'id':'u1'}).findChilren('a',{'class':'mnav'})
values=[]
for atag in atags:
   values.append(atag.text)
以上程序即可实现我们的要求,python解析html的还有一个scrapy框架的xpath,以后分享scrapy时再讲。
<html>
<head>
<meta http-equiv=content-type content=text/html;charset=utf-8>
<meta http-equiv=X-UA-Compatible content=IE=Edge>
<meta content=always name=referrer>
<link rel=stylesheet type=text/css href=http://s1.bdstatic.com/r/www/cache/bdorz/baidu.min.css>
<title>百度一下,你就知道</title></head>
<body link=#0000cc>
<div id=wrapper>
<div id=head>
<div > <div > <div > <div id=lg><img hidefocus=true src=//www.baidu.com/img/bd_logo1.png width=270 height=129></div>
<form id=form name=f action=//www.baidu.com/s > <input type=hidden name=ie value=utf-8> <input type=hidden name=f value=8> <input type=hidden
name=rsv_bp
value=1>
<input type=hidden name=rsv_idx value=1> <input type=hidden name=tn value=baidu><span
><input id=kw name=wd > autocomplete=off autofocus></span><span
><input type=submit id=su value=百度一下 ></span></form>
</div>
</div>
<div id=u1><a href=http://news.baidu.com name=tj_trnews > name=tj_trhao123 > <a href=http://map.baidu.com name=tj_trmap > > href=http://tieba.baidu.com name=tj_trtieba > <noscript><a
href=http://www.baidu.com/bdorz/login.gif?login&tpl=mn&u=http%3A%2F%2Fwww.baidu.com%2f%3fbdorz_come%3d1
name=tj_login > <script>document.write('<a href="http://www.baidu.com/bdorz/login.gif?login&tpl=mn&u=' + encodeURIComponent(window.location.href + (window.location.search === "" ? "?" : "&") + "bdorz_come=1") + '" name="tj_login" >登录</a>');</script>
<a href=//www.baidu.com/more/ name=tj_briicon > </div>
</div>
<div id=ftCon>
<div id=ftConw><p id=lh><a href=http://home.baidu.com>关于百度</a> <a href=http://ir.baidu.com>About Baidu</a></p>
<p id=cp>©2017 Baidu <a href=http://www.baidu.com/duty/>使用百度前必读</a>  <a
href=http://jianyi.baidu.com/ > src=//www.baidu.com/img/gs.gif></p></div>
</div>
</div>
</body>
</html>


(3) re 
re正则模块很强大,有match search sub replace这些api,每个都有自己的特长,可以参考:http://www.runoob.com/python3/python3-reg-expressions.html
(4) sqlalchemy
一款python的数据库orm框架,用了下,很好用,有点类似于java 的hibernate,但更灵活。
说了这么多,该帖下爬虫脚本的代码了,下面是目录结构,毕竟也是专业程序员,不能写的一团糟,也要讲究架构,哈哈。
------youku_any #包名
--------------datasource.py #专门管理数据源session
--------------youkubannerdao.py #程序里抓取的优酷banner信息,这个是dao层
--------------youkuservice.py   #不用说了,业务逻辑
还有一件事情,就是建表,不多说了:
CREATE TABLE `youku_banner` (
  `id` bigint(22) NOT NULL AUTO_INCREMENT,
  `type` int(2) NOT NULL, #优酷banner类型 1:电视 2:电影 3.综艺 
  `year` int(4) NOT NULL,
  `month` int(2) NOT NULL,
  `date` int(2) NOT NULL,
  `hour` int(2) NOT NULL,
  `minute` int(2) NOT NULL,
  `img` varchar(255) DEFAULT NULL,
  `title` varchar(255) DEFAULT NULL,
  `url` varchar(255) DEFAULT NULL,
  `create_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  KEY `idx_uniq` (`year`,`month`,`date`,`hour`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=83 DEFAULT CHARSET=utf8mb4
接下来就是代码实现了:
datasource.py
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

dburl = 'mysql+pymysql://root:123@localhost/youku?charset=utf8'
#pool_size 置为100 session回收时间3600s
ds = create_engine(dburl,pool_size=100,pool_recycle=3600)

Session = sessionmaker(bind=ds)
# session=Session()

#创建session管理类
class SessionManager():

    def __init__(self):
        self.session=Session()

    def __enter__(self):
        return self.session
    #连接池管理session,不需要显示close
    def __exit__(self, exc_type, exc_val, exc_tb):
        # session.close()
        print('not close')
youkubannerdao.py
from sqlalchemy import Sequence, Column, Integer, BigInteger, String, TIMESTAMP, text
from sqlalchemy.ext.declarative import declarative_base
from youku_any.datasource import SessionManager

Base = declarative_base()

#继承基类Base
class YoukuBanner(Base):

    #指定表名
    __tablename__ = 'youku_banner'

    #定义字段映射关系
    id = Column(BigInteger, Sequence('id'), primary_key=True)
    type=Column(Integer)
    year = Column(Integer)
    month = Column(Integer)
    date = Column(Integer)
    hour = Column(Integer)
    minute = Column(Integer)
    img = Column(String(255))
    title = Column(String(255))
    url = Column(String(255))
    createTime = Column('create_time', TIMESTAMP)


    def add(self):
        #with as 先执行SessionManager __enter__() 逻辑行结束执行__exit()__
        with SessionManager() as session:
            try:
                session.add(self)
                session.commit()
            except:
                session.rollback()

    def addBatch(self,values):
        with SessionManager() as session:
            try:
                session.add_all(values)
                session.commit()
            except:
                session.rollback()


    def select(self,param):
        with SessionManager() as session:
            return session.query(YoukuBanner).select_from(YoukuBanner).filter(param)

    def remove(self,parma):
        with SessionManager() as session:
            try:
                session.query(YoukuBanner).filter(parma).delete(synchronize_session='fetch')
                session.commit()
            except:
                session.rollback()

    def update(self,param,values):
        with SessionManager() as session:
            try:
                session.query(YoukuBanner).filter(param).update(values, synchronize_session='fetch')
                session.commit()
            except:
                session.rollback()
youkuservice.py
import requests
import json
import re
import datetime
from bs4 import BeautifulSoup
from sqlalchemy import text

from youku_any.youkubannerdao import YoukuBanner

def getsoup(url):
    with requests.get(url, params=None, headers=None) as req:
        if req.encoding != 'utf-8':
            encodings = requests.utils.get_encodings_from_content(req.text)
            if encodings:
                encode = encodings[0]
            else:
                encode = req.apparent_encoding
        encode_content = req.content.decode(encode).encode('utf-8')
        soup = BeautifulSoup(encode_content, 'html.parser')
        return soup


def getbanner(soup):
    # soup = BeautifulSoup()
    # soup.findChild()
    bannerDivP = soup.find('div', {'id': 'm_86804', 'name': 'm_pos'})
    bannerScript = bannerDivP.findChildren('script', {'type': 'text/javascript'})[1].text
    m = re.search('\[.*\]', bannerScript)
    banners = json.loads(m.group())
    for banner in banners:
        time = datetime.datetime.now()
        youkubanner = YoukuBanner(type=1, year=time.year, month=time.month, date=time.day, hour=time.hour,
                                  minute=time.minute,
                                  img=banner['img'], title=banner['title'], url=banner['url'])
        youkubanner.add()

soup=getsoup('http://tv.youku.com/')
getbanner(soup)

youkuBanner = YoukuBanner()
youkuBanner.remove(parma=text('id=67 or id=71'))
youkuBanner.update(param=text('id=70'),values={'title':YoukuBanner.title + '呼啸山庄'})

for i in range(0,10000):
    youkuBanner.update(param=text('id=70'), values={'title': YoukuBanner.title + '呼啸山庄'})
    bannerList = youkuBanner.select(param=text('id > 66 and id < 77 order by id asc limit 0,7'))
    print("lines--------%d" % i)
    # time.sleep(10)
    for banner in bannerList:
        print(banner.id,banner.minute,banner.img,banner.title)
到此,一个简答的爬虫脚本就写完了,周末两天的成果还是有点小满足,不过这只是python的冰山一脚,还有好多等着我们去探讨呢。



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