python中删除爬取数据的网页元素 python爬虫数据去重

python爬虫的去重策略

1、将访问过的url保存到数据库中

2、将访问过的url保存到set中

优点：只需要 o(1)的代价就可以查询 URL

缺点：对内存要求高。若有 1 亿网页，则占用内存为：1000000000*2byte*50 个字符/1024/1024/1024 = 9G

3、URL 经过 md5 等方法哈希后保存到 set 中

优点：可以成倍降低内存占用，Scrapy 使用的这种方法

4、用bitmap或者bloomfilter方法，将访问过的URL通过hash函数映射到某一位

bitmap 方法优点：一亿 URL 占用约 12M

bitmap 方法：去重没那么精准，存在冲突。

bloomfilter 优点：对 bitmap 进行改进，多重 hash 函数降低冲突

第一种方法案例

import requests
from bs4 import BeautifulSoup
import re
import pymongo


class KongjieSpider:
    def __init__(self):
        server = 'localhost'
        port = '27017'
        dbname = 'admin'
        user = 'admin'
        pwd = '123'
        uri = 'mongodb://' + user + ':' + pwd + '@' + server + ':' + port + '/' + dbname
        client = pymongo.MongoClient(uri)  ##与MongDB建立连接
        db = client['dbkongjie1805']  ## 选择一个数据库
        self.kongjie_collection = db['kongjie']  ##在数据库中，选择一个集合

    def getUA(self):
        user_agent = 'Mozilla/5.0 (compatible; WOW64; MSIE 10.0; Windows NT 6.2)'
        headers = {'User-Agent': user_agent}
        return headers

    def parse_album_url(self,url):
        """
        解析出相册url，然后进入相册爬取图片
        """
        headers = self.getUA()
        response = requests.get(url, headers=headers)
        soup = BeautifulSoup(response.text, 'lxml')
        people_list = soup.select('div.ptw > ul > li')
        for people in people_list:
            self.save_images_in_album(people.div.a['href'])

        #爬取下一页
        next_page = soup.select_one('a.nxt')
        if next_page:
            self.parse_album_url(next_page['href'])
        else:
            print('下载结束！')

    def save_images_in_album(self,album_url):
        """
        进入空姐网用户的相册，开始一张一张的保存相册中的图片。
        """
        headers = self.getUA()
        response = requests.get(album_url, headers=headers)
        soup = BeautifulSoup(response.text, 'lxml')
        ls = soup.select('ul.ptw.ml.mlp.cl > li')
        if len(ls)>0:
            print('len ',len(ls))
            for item in ls:
                # 提取照片页面的url
                url = item.select_one('a')['href']
                #去重操作
                if self.kongjie_collection.find_one({'img_url': url}):  ##判断这个主题是否已经在数据库中、不在就运行else下的内容，在则忽略。
                    print(u'这个页面已经爬取过了')
                else:
                    pat = re.compile(r'uid=(\d+)&.*?picid=(\d+)')
                    matchObj = pat.search(url)
                    uid = matchObj.group(1)
                    picid = matchObj.group(2)
                    print('uid:',uid)
                    print('picid:',picid)
                    # 打开照片页面,提取image的src属性
                    response = requests.get(url, headers=headers)
                    soup1 = BeautifulSoup(response.text, 'lxml')
                    img_url = soup1.select_one('div#photo_pic > a > img')['src']
                    # 下载图片
                    response = requests.get(img_url, headers=headers)
                    imgName = './images/'+ uid + picid +'.jpg'
                    with open(imgName,'wb') as file:
                        file.write(response.content)
                    self.kongjie_collection.save({'img_url': url})

            ls = soup.select('a.nxt')
            print('next_page: ',len(ls))
            if len(ls)>0:
                next_page_url = ls[0]['href']
                print('next_page_url:',next_page_url)
                save_images_in_album(next_page_url)


if __name__ == '__main__':
    start_url='http://www.kongjie.com/home.php?mod=space&do=album&view=all&page=1'
    spider = KongjieSpider()
    spider.parse_album_url(start_url)

第二种案例：

import requests
from bs4 import BeautifulSoup
import re
import pymongo


class KongjieSpider:
    def __init__(self):
        server = 'localhost'
        port = '27017'
        dbname = 'admin'
        user = 'admin'
        pwd = '123'
        uri = 'mongodb://' + user + ':' + pwd + '@' + server + ':' + port + '/' + dbname
        client = pymongo.MongoClient(uri)  ##与MongDB建立连接（这是默认连接本地MongDB数据库）
        db = client['dbkongjie']  ## 选择一个数据库
        self.kongjie_collection = db['kongjie']  ##在数据库中，选择一个集合
        self.img_urls = set()  ##初始化一个集合 用来保存图片地址


    def getUA(self):
        user_agent = 'Mozilla/5.0 (compatible; WOW64; MSIE 10.0; Windows NT 6.2)'
        headers = {'User-Agent': user_agent}
        return headers


    def parse_album_url(self,url):
        """
        解析出相册url，然后进入相册爬取图片
        """
        headers = self.getUA()
        response = requests.get(url, headers=headers)
        soup = BeautifulSoup(response.text, 'lxml')
        people_list = soup.select('div.ptw > ul > li')
        for people in people_list:
            self.save_images_in_album(people.div.a['href'])

        #爬取下一页
        next_page = soup.select_one('a.nxt')
        if next_page:
            self.parse_album_url(next_page['href'])
        else:
            print('下载结束！')


    def save_images_in_album(self,album_url):
        """
        进入空姐网用户的相册，开始一张一张的保存相册中的图片。
        """
        headers = self.getUA()
        response = requests.get(album_url, headers=headers)
        soup = BeautifulSoup(response.text, 'lxml')
        ls = soup.select('ul.ptw.ml.mlp.cl > li')
        if len(ls)>0:
            print('len ',len(ls))
            for item in ls:
                # 提取照片页面的url
                url = item.select_one('a')['href']
                #去重操作
                if url in self.img_urls:  ##判断照片页面的url是否已经存在于集合中，不在就运行else下的内容，在则忽略。
                    print(u'这个页面已经爬取过了')
                else:
                    pat = re.compile(r'uid=(\d+)&.*?picid=(\d+)')
                    matchObj = pat.search(url)
                    uid = matchObj.group(1)
                    picid = matchObj.group(2)
                    print('uid:',uid)
                    print('picid:',picid)
                    # 打开照片页面,提取image的src属性
                    response = requests.get(url, headers=headers)
                    soup1 = BeautifulSoup(response.text, 'lxml')
                    img_url = soup1.select_one('div#photo_pic > a > img')['src']
                    # 下载图片
                    response = requests.get(img_url, headers=headers)
                    imgName = './images/'+ uid + picid +'.jpg'
                    with open(imgName,'wb') as file:
                        file.write(response.content)
                    self.img_urls.add(url)  # 把url添加到集合中
                    print('count:',len(self.img_urls))

            ls = soup.select('a.nxt')
            print('next_page: ',len(ls))
            if len(ls)>0:
                next_page_url = ls[0]['href']
                print('next_page_url:',next_page_url)
                save_images_in_album(next_page_url)


if __name__ == '__main__':
    start_url='http://www.kongjie.com/home.php?mod=space&do=album&view=all&page=1'
    spider = KongjieSpider()
    spider.parse_album_url(start_url)

第三种案例

import requests
from bs4 import BeautifulSoup
import re
import pymongo
from hashlib import md5

class KongjieSpider:
    def __init__(self):
        server = 'localhost'
        port = '27017'
        dbname = 'admin'
        user = 'admin'
        pwd = '123'
        uri = 'mongodb://' + user + ':' + pwd + '@' + server + ':' + port + '/' + dbname
        client = pymongo.MongoClient(uri)  ##与MongDB建立连接（这是默认连接本地MongDB数据库）
        db = client['dbkongjie']  ## 选择一个数据库
        self.kongjie_collection = db['kongjie']  ##在数据库中，选择一个集合
        self.img_urls = set()  ##初始化一个集合 用来保存图片地址


    def getUA(self):
        user_agent = 'Mozilla/5.0 (compatible; WOW64; MSIE 10.0; Windows NT 6.2)'
        headers = {'User-Agent': user_agent}
        return headers


    def parse_album_url(self,url):
        """
        解析出相册url，然后进入相册爬取图片
        """
        headers = self.getUA()
        response = requests.get(url, headers=headers)
        soup = BeautifulSoup(response.text, 'lxml')
        people_list = soup.select('div.ptw > ul > li')
        for people in people_list:
            self.save_images_in_album(people.div.a['href'])

        #爬取下一页
        next_page = soup.select_one('a.nxt')
        if next_page:
            self.parse_album_url(next_page['href'])
        else:
            print('下载结束！')


    def save_images_in_album(self,album_url):
        """
        进入空姐网用户的相册，开始一张一张的保存相册中的图片。
        """
        headers = self.getUA()
        response = requests.get(album_url, headers=headers)
        soup = BeautifulSoup(response.text, 'lxml')
        ls = soup.select('ul.ptw.ml.mlp.cl > li')
        if len(ls)>0:
            print('len ',len(ls))
            for item in ls:
                # 提取照片页面的url
                url = item.select_one('a')['href']
                #去重操作
                hash_md5 = md5(url.encode('utf8'))
                hash_str = hash_md5.hexdigest()
                if hash_str in self.img_urls:  ##判断照片页面的url是否已经存在于集合中，不在就运行else下的内容，在则忽略。
                    print(u'这个页面已经爬取过了')
                else:
                    pat = re.compile(r'uid=(\d+)&.*?picid=(\d+)')
                    matchObj = pat.search(url)
                    uid = matchObj.group(1)
                    picid = matchObj.group(2)
                    print('uid:',uid)
                    print('picid:',picid)
                    # 打开照片页面,提取image的src属性
                    response = requests.get(url, headers=headers)
                    soup1 = BeautifulSoup(response.text, 'lxml')
                    img_url = soup1.select_one('div#photo_pic > a > img')['src']
                    # 下载图片
                    response = requests.get(img_url, headers=headers)
                    imgName = './images/'+ uid + picid +'.jpg'
                    with open(imgName,'wb') as file:
                        file.write(response.content)

                    self.img_urls.add(hash_str)
                    print('count:',len(self.img_urls),hash_str)

            ls = soup.select('a.nxt')
            print('next_page: ',len(ls))
            if len(ls)>0:
                next_page_url = ls[0]['href']
                print('next_page_url:',next_page_url)
                save_images_in_album(next_page_url)


if __name__ == '__main__':
    start_url='http://www.kongjie.com/home.php?mod=space&do=album&view=all&page=1'
    spider = KongjieSpider()
    spider.parse_album_url(start_url)

第四种案例

import requests
from bs4 import BeautifulSoup
import re
import pymongo
from pybloom_live import ScalableBloomFilter


class KongjieSpider:
    def __init__(self):
        server = 'localhost'
        port = '27017'
        dbname = 'admin'
        user = 'admin'
        pwd = '123'
        uri = 'mongodb://' + user + ':' + pwd + '@' + server + ':' + port + '/' + dbname
        client = pymongo.MongoClient(uri)  ##与MongDB建立连接（这是默认连接本地MongDB数据库）
        db = client['dbkongjie']  ## 选择一个数据库
        self.kongjie_collection = db['kongjie']  ##在数据库中，选择一个集合
        self.sbf = ScalableBloomFilter(initial_capacity=100, error_rate=0.001, mode=ScalableBloomFilter.LARGE_SET_GROWTH)

    def getUA(self):
        user_agent = 'Mozilla/5.0 (compatible; WOW64; MSIE 10.0; Windows NT 6.2)'
        headers = {'User-Agent': user_agent}
        return headers

    def parse_album_url(self,url):
        """
        解析出相册url，然后进入相册爬取图片
        """
        headers = self.getUA()
        response = requests.get(url, headers=headers)
        soup = BeautifulSoup(response.text, 'lxml')
        people_list = soup.select('div.ptw > ul > li')
        for people in people_list:
            self.save_images_in_album(people.div.a['href'])

        #爬取下一页
        next_page = soup.select_one('a.nxt')
        if next_page:
            self.parse_album_url(next_page['href'])
        else:
            print('下载结束！')

    def save_images_in_album(self,album_url):
        """
        进入空姐网用户的相册，开始一张一张的保存相册中的图片。
        """
        headers = self.getUA()
        response = requests.get(album_url, headers=headers)
        soup = BeautifulSoup(response.text, 'lxml')
        ls = soup.select('ul.ptw.ml.mlp.cl > li')
        if len(ls)>0:
            print('len ',len(ls))
            for item in ls:
                # 提取照片页面的url
                url = item.select_one('a')['href']
                #去重操作
                if url in self.sbf:  ##判断照片页面的url是否已经存在于集合中，不在就运行else下的内容，在则忽略。
                    print(u'这个页面已经爬取过了')
                else:
                    pat = re.compile(r'uid=(\d+)&.*?picid=(\d+)')
                    matchObj = pat.search(url)
                    uid = matchObj.group(1)
                    picid = matchObj.group(2)
                    print('uid:',uid)
                    print('picid:',picid)
                    # 打开照片页面,提取image的src属性
                    response = requests.get(url, headers=headers)
                    soup1 = BeautifulSoup(response.text, 'lxml')
                    img_url = soup1.select_one('div#photo_pic > a > img')['src']
                    # 下载图片
                    response = requests.get(img_url, headers=headers)
                    imgName = './images/'+ uid + picid +'.jpg'
                    with open(imgName,'wb') as file:
                        file.write(response.content)

                    self.sbf.add(url)
                    print('count:',len(self.sbf))

            ls = soup.select('a.nxt')
            print('next_page: ',len(ls))
            if len(ls)>0:
                next_page_url = ls[0]['href']
                print('next_page_url:',next_page_url)
                save_images_in_album(next_page_url)


if __name__ == '__main__':
    start_url='http://www.kongjie.com/home.php?mod=space&do=album&view=all&page=1'
    spider = KongjieSpider()
    spider.parse_album_url(start_url)