用python编写简单爬虫

需求：抓取百度百科python词条相关词条网页的标题和简介，并将数据输出在一个html表格中

入口页:python的百度词条页 https://baike.baidu.com/item/Python/407313

词条页面URL：'/item/%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%A8%8B%E5%BA%8F%E8%AE%BE%E8%AE%A1%E8%AF%AD%E8%A8%80' 注意:这不是一个完整的url,需要对之进行拼接

数据格式：

 -标题：<dd class="lemmaWgt-lemmaTitle-title"><h1>***</h1></dd>
 -简介：<div class='lemma-summary'>***</div> 
 页面编码：UTF-8

实例代码：
文件目录结构如图



入口文件（spider_main.py）：

# coding:utf-8

import url_manager

import html_parser

import html_downloader

import html_outputer

class SpiderMain(object):

    def __init__(self):

        self.urls = url_manager.UrlManager()

        self.downloader = html_downloader.HtmlDownloader()

        self.parser = html_parser.HtmlParser()

        self.outputer = html_outputer.HtmlOutputer()

    def craw(self, root_url):

        count = 1

        self.urls.add_new_url(root_url)

        while self.urls.has_new_url():  # 如果有待爬取的url

            try:

                new_url = self.urls.get_new_url()  # 取一个待爬取的url

                print 'craw %d:%s' % (count, new_url)

                html_cont = self.downloader.download(new_url)  # 下载页面

                new_urls, new_data = self.parser.parse(new_url, html_cont)  # 解析页面得到新的url和一些数据

                self.urls.add_new_urls(new_urls)  # 将新得到的url添加到url管理器

                self.outputer.collect_data(new_data)  # 将获取到的数据添加到output文件中

                if count == 10:

                    break

                count += 1

            except Exception as e:

                print e

        self.outputer.output_html()

if __name__ == '__main__':

    obj_spider = SpiderMain()

    obj_spider.craw('https://baike.baidu.com/item/Python/407313')

url管理文件（url_manager.py）:

# coding:utf-8

class UrlManager(object):

    def __init__(self):

        self.new_urls = set()

        self.old_urls = set()

    def add_new_url(self, url):

        if url is None:

            return

        if url not in self.new_urls and url not in self.old_urls:

            self.new_urls.add(url)

    def add_new_urls(self, urls):

        if urls is None or len(urls) == 0:

            return

        for url in urls:

            self.add_new_url(url)

    def has_new_url(self):

        return len(self.new_urls) != 0

    def get_new_url(self):

        new_url = self.new_urls.pop()  # 从列表中获取一个并且移除

        self.old_urls.add(new_url)

        return new_url

页面源码下载（html_downloader.py）:

# coding:utf-8

import urllib2

class HtmlDownloader(object):

    def download(self, url):

        if url is None:

            return None

        response = urllib2.urlopen(url)

        if response.getcode() != 200:

            return None

        return response.read()

源码解析（html_parser.py）:

# coding:utf-8

from bs4 import BeautifulSoup

import urlparse

import re

class HtmlParser(object):

    def _get_new_urls(self, page_url, soup):

        new_urls = set()

        # 页面中的链接格式：/item/xxx

        links = soup.find_all('a', href=re.compile(r"/item/(.*)"))  # 得到所有的url的标签

        for link in links:

            new_url = link['href']  # 获取所有的链接

            new_full_url = urlparse.urljoin(page_url, new_url)  # 让new_url按照page_url的格式拼接成一个完整的url

            new_urls.add(new_full_url)

        return new_urls

    def _get_new_data(self, page_url, soup):

        res_data = {}

        res_data['url'] = page_url

        # <dd class="lemmaWgt-lemmaTitle-title"><h1>Python</h1></dd>

        title_node = soup.find('dd', class_='lemmaWgt-lemmaTitle-title').find('h1')

        res_data['title'] = title_node.get_text()

        # <div class="lemma-summary" label-module="lemmaSummary">    简介的html

        summary_node = soup.find('div', class_='lemma-summary')

        res_data['summary'] = summary_node.get_text()

        return res_data

    def parse(self, page_url, html_cont):

        if page_url is None or html_cont is None:

            return

        soup = BeautifulSoup(html_cont, 'html.parser', from_encoding='utf-8')

        new_urls = self._get_new_urls(page_url, soup)

        new_data = self._get_new_data(page_url, soup)

        return new_urls, new_data

将爬取到的数据输出（html_output.py）:

# coding:utf-8

class HtmlOutputer(object):

    def __init__(self):

        self.datas = []

    def collect_data(self, data):  # 收集数据

        if data is None:

            return

        self.datas.append(data)

    def output_html(self):  # 将数据输出为html

        fout = open('output.html', 'w')

        fout.write('<html>')

        fout.write('<body>')

        fout.write('<table>')

        for data in self.datas:

            fout.write('<tr>')

            fout.write('<td>%s</td>' % data['url'])

            fout.write('<td>%s</td>' % data['title'].encode('utf-8'))

            fout.write('<td>%s</td>' % data['summary'].encode('utf-8'))

            fout.write('</tr>')

        fout.write('</table>')

        fout.write('</body>')

        fout.write('</html>')

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用python编写简单爬虫

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