关于python爬虫程序中途停止的问题

# -*- coding: utf-8 -*-

"""

Created on Fri Aug 11 16:31:42 2017

@author: lart

"""



import urllib.request

import re, time





def req_open_html(url):

    print('req_open_html begin')

    headers = {'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:55.0) Gecko/20100101 Firefox/55.0'}

    request = urllib.request.Request(url, headers=headers)

    html = urllib.request.urlopen(request).read().decode('GBK')

    print('req_open_html end')

    return html



def re_find_match(re_string, operation, html):

    print('re_find_match begin')

    pattern = re.compile(re_string, re.I)

    if operation == 'findall':

        result = pattern.findall(html)

    elif operation ==  'match':

        result = pattern.match(html)

    else:

        print('this operation is invalid')

        exit(-1)

    print('re_find_match end')

    return result





if __name__ == '__main__':

    url_base = 'http://www.7kankan.la/book/1/'

    html = req_open_html(url_base)

    findall_title = re_find_match(r'<title>(.+?)</title>', 'findall', html)

    findall_article = re_find_match(r'<dd class="col-md-3"><a href=[\',"](.+?)[\',"] title=[\',"](.+?)[\',"]>', 'findall', html)



    with open(findall_title[0] + '.txt', 'w+', encoding='utf-8') as open_file:

        print('article文件打开', findall_article)

        for i in range(len(findall_article)):

            print(i)

            open_file.write(findall_article[i][1] + '\n ---------------------------------------------- \n')

            url_arctile = url_base + findall_article[i][0]

            html_article = req_open_html(url_arctile)

            findall_article_txet = re_find_match(r'    (.+?)<br />', 'findall', html_article)

            findall_article_next = findall_article[i][0].replace('.html', '_2.html')

            url_arctile_next = url_base + findall_article_next

            html_article_next = req_open_html(url_arctile_next)

            if html_article_next:

                findall_article_txet.extend(re_find_match(r'    (.+?)<br />', 'findall', html_article_next))

                for text in findall_article_txet:

                    open_file.write(text + '\n')

            time.sleep(1)



    print('文件写入完毕')