阅读《Practical web scraping for data science》p161的代码之 Cannot operate on a closed database错误

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问题描述

最近阅读了一本爬虫方面的书¹，按照书上161页的代码原封不动的敲到电脑中，编写一个爬虫蜘蛛，但运行以后出现以下错误：

Error closing cursor
Traceback (most recent call last):
File “E:\StudyCard\BigData\WebScrape\PWSfDScode.pwsenv\lib\site-packages\sqlalchemy\engine\result.py”, line 1324, in fetchone
row = self._fetchone_impl()
File “E:\StudyCard\BigData\WebScrape\PWSfDScode.pwsenv\lib\site-packages\sqlalchemy\engine\result.py”, line 1204, in _fetchone_impl
return self.cursor.fetchone()
sqlite3.ProgrammingError: Cannot operate on a closed database.
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File “E:\StudyCard\BigData\WebScrape\PWSfDScode.pwsenv\lib\site-packages\sqlalchemy\engine\base.py”, line 1339, in _safe_close_cursor
cursor.close()
sqlite3.ProgrammingError: Cannot operate on a closed database.
Traceback (most recent call last):
File “E:\StudyCard\BigData\WebScrape\PWSfDScode.pwsenv\lib\site-packages\sqlalchemy\engine\result.py”, line 1324, in fetchone
row = self._fetchone_impl()
File “E:\StudyCard\BigData\WebScrape\PWSfDScode.pwsenv\lib\site-packages\sqlalchemy\engine\result.py”, line 1204, in _fetchone_impl
return self.cursor.fetchone()
sqlite3.ProgrammingError: Cannot operate on a closed database.

我记得之前看这本书的时候就遇到过该错误。该错误产生的原因应该是records库的原因。

解决方案

需要在建立数据库的代码后添加代码：

import requests
import records
from bs4 import BeautifulSoup
from urllib.parse import urljoin
from sqlalchemy.exc import IntegrityErrordb = records.Database('sqlite:///crawler_database.db')
db = db.get_connection() # 新加