Python实现爬虫从网络上下载文档

Posted 2020-11-17 hasan

最近在学习Python，自然接触到了爬虫，写了一个小型爬虫软件，从初始Url解析网页，使用正则获取待爬取链接，使用beautifulsoup解析获取文本，使用自己写的输出器可以将文本输出保存，具体代码如下：

Spider_main.py

# coding:utf8
from baike_spider import url_manager, html_downloader, html_parser, 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():
            print("self.urls.has %s" % self.urls.new_urls)
            try:
                new_url = self.urls.get_new_url()
                print("craw %d : %s"%(count, new_url))
                html_cont = self.downloader.download(new_url)
                new_urls, new_data = self.parser.parse(new_url, html_cont)
                self.urls.add_new_urls(new_urls)
                self.outputer.collect_data(new_data)

                if count == 1000:
                    break

                count = count + 1
            except:
                print("craw failed")

        self.outputer.output_html()
        self.outputer.output_txt()


if __name__ == ‘__main__‘:
    root_url = "http://www.shushu8.com/jiangnan/longzu2qianzhuan/1"
    obj_spider = SpiderMain()
    obj_spider.craw(root_url)

url_manager.py

class UrlManager(object):
    def __init__(self):
        self.new_urls = set()
        self.old_urls = set()

    def add_new_url(self, url):
        print(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 has_new_url(self):
        return len(self.new_urls) != 0

    def get_new_url(self):
        new_url = self.new_urls.pop()
        self.old_urls.add(new_url)
        # print(‘new url is %s‘ % new_url)
        return new_url

    def add_new_urls(self, urls):
        print("add_new_urls %s" % urls)
        if urls is None or len(urls) == 0:
            return
        for url in urls:
            self.add_new_url(url)
            print(url)

html_parser.py

import re
import urllib.parse
from bs4 import BeautifulSoup


class HtmlParser(object):

    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)
        print("parse new_urls %s" % new_urls)
        new_data = self._get_new_data(page_url, soup)
        return new_urls, new_data

    def _get_new_data(self, page_url, soup):
        res_data = {}

        res_data[‘url‘] = page_url
        print(page_url)

        title_node = soup.find(class_="title").find("h1")
        print(title_node.get_text())
        res_data[‘title‘] = title_node.get_text()

        print("_get_new_data")

        summary_node = soup.find(‘pre‘)
        print(summary_node.get_text())
        res_data[‘summary‘] = summary_node.get_text()


        return res_data

    def _get_new_urls(self, page_url, soup):
        new_urls = set()
        links = soup.find_all(‘a‘, href=re.compile(r"/jiangnan/"))
        print(links)
        for link in links:
            new_url = link[‘href‘]
            new_full_url = urllib.parse.urljoin(page_url, new_url)
            new_urls.add(new_full_url)
            # print(new_full_url)
        return new_urls

html_downloader.py

import urllib.request


class HtmlDownloader(object):

    def download(self, url):
        if url is None:
            return None
        response = urllib.request.urlopen(url)
        if response.getcode() != 200:
            return None

        return response.read()

html_outputer.py

class HtmlOutputer(object):
    def __init__(self):
        self.datas = []

    def collect_data(self, data):
        if data is None:
            return
        self.datas.append(data)

    def output_txt(self):
        fout = open(‘output.txt‘, ‘w‘, encoding=‘utf-8‘)
        for data in self.datas:
            fout.write(‘%s 
‘ % data[‘title‘])
            fout.write(‘%s 
‘ % data[‘summary‘])

    def output_html(self):
        fout = open(‘output.html‘, ‘w‘, encoding=‘utf-8‘)
        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‘])
            fout.write(‘<td>%s</td>‘ % data[‘summary‘])
            fout.write(‘</tr>‘)

        fout.write(‘</table>‘)
        fout.write(‘</body>‘)
        fout.write(‘</html>‘)

        fout.close()