本地运行正常，PythonAnywhere数据库无法填充的问题排查

我在PythonAnywhere上已有数据库及对应凭证，目标是爬取多个新闻网站的数据，并通过Flask将数据展示到新网站。以下是网站的一段代码（已省略可正常运行的导入部分）：

@app.route("/nationals")
def scrape_nationals():
    feeds = [{"type": "news","title": "BBC", "url": "http://feeds.bbci.co.uk/news/uk/rss.xml"},
        {"type": "news","title": "The Economist", "url": "https://www.economist.com/international/rss.xml"},
        {"type": "news","title": "The New Statesman", "url": "https://www.newstatesman.com/feed"},
        {"type": "news","title": "The New York Times", "url": "https://rss.nytimes.com/services/xml/rss/nyt/HomePage.xml"},
        {"type": "news","title": "Metro UK","url": "https://metro.co.uk/feed/"},
        {"type": "news", "title": "Evening Standard", "url": "https://www.standard.co.uk/rss.xml"},
        {"type": "news","title": "Daily Mail", "url": "https://www.dailymail.co.uk/articles.rss"},
        {"type": "news","title": "Sky News", "url": "https://news.sky.com/feeds/rss/home.xml"},
        {"type": "news","title": "The Mirror", "url": "https://www.mirror.co.uk/news/?service=rss"},
        {"type": "news","title": "The Sun", "url": "https://www.thesun.co.uk/news/feed/"},
        {"type": "news", "title": "Sky News", "url": "https://news.sky.com/feeds/rss/home.xml"},
        {"type": "news", "title": "The Guardian", "url": "https://www.theguardian.com/uk/rss"},
        {"type": "news", "title": "The Independent", "url": "https://www.independent.co.uk/news/uk/rss"},
        #{"type": "news", "title": "The Telegraph", "url": "https://www.telegraph.co.uk/news/rss.xml"},
        {"type": "news", "title": "The Times", "url": "https://www.thetimes.co.uk/?service=rss"}]
    print(feeds)

    data = []                               # <---- initialize empty list here
    for feed in feeds:
        parsed_feed = feedparser.parse(feed['url'])
        #print("Title:", feed['title'])
        #print("Number of Articles:", len(parsed_feed.entries))
        #print("
")
        for entry in parsed_feed.entries:

            title = entry.title
            print(title)
            url = entry.link
            #print(entry.summary)
            try:
                summary = entry.summary[:400] or "No summary available" # I simplified the ternary operators here
            except:
                #print("no summary")
                summary = "none"
            try:
                date = pd.to_datetime(entry.published)#
                #or "No data available"     # I simplified the ternary operators here
            except:
                #print("date")
                date = pd.to_datetime("01-01-1970")
            data.append([title, url, summary, date])          # <---- append data from each entry here

    df = pd.DataFrame(data, columns = ['title', 'url', 'summary', 'date'])
    articles = pd.read_sql('nationals', con = engine)
    articles = articles.drop_duplicates()
    df = df.append(articles)
    df = df.drop_duplicates()
    df.to_sql('nationals', con = engine, if_exists = 'replace', index = False)

这段代码在本地VSCode中运行正常，但无法填充PythonAnywhere上的nationals表，请问问题出在哪里？

• 数据库连接配置错误
  PythonAnywhere的数据库连接字符串和本地差异很大，本地可能用SQLite或本地MySQL，而PythonAnywhere要求特定格式：比如MySQL需用mysql+pymysql://username:password@username.mysql.pythonanywhere-services.com/username$database_name。检查你的engine配置是否完全匹配，尤其注意数据库名带$前缀（如yourusername$nationals_db），用户名、密码有没有输错。

• 网络访问限制
  PythonAnywhere免费账户对外访问有部分限制，部分RSS源可能屏蔽了平台IP，或者请求被目标网站识别为非浏览器请求导致拦截。可以在PythonAnywhere控制台手动执行feedparser.parse("目标RSS链接")测试能否获取内容；若失败，要么更换RSS源，要么给feedparser添加请求头模拟浏览器，比如：

  parsed_feed = feedparser.parse(feed['url'], request_headers={'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118.0.0.0 Safari/537.36'})
  

• 静默异常导致流程中断
  代码中的try-except块过于宽泛，没有捕获具体异常，爬取或数据库操作出错时无法察觉。建议把except:改为except Exception as e:并打印异常信息，比如：

  try:
      summary = entry.summary[:400] or "No summary available"
  except Exception as e:
      print(f"获取摘要失败: {str(e)}")
      summary = "none"
  

  另外，可查看PythonAnywhere的Web应用日志（页面"Logs"选项卡），里面会记录运行时的报错详情。

• Pandas版本兼容性问题
  本地与PythonAnywhere的Pandas版本可能不一致，df.append()在Pandas 2.0+已被弃用，若PythonAnywhere上的版本为2.0+，该语句会报错，导致后续数据库写入未执行。建议替换为Pandas推荐的pd.concat写法：

  df = pd.concat([df, articles], ignore_index=True)
  

• 数据库权限不足
  检查PythonAnywhere上的数据库用户是否拥有CREATE、INSERT、REPLACE权限，权限不足会导致to_sql的if_exists='replace'执行失败。可在PythonAnywhere数据库管理页面查看用户权限，或手动执行SQL语句测试修改表的权限。

• 请求超时中断执行
  PythonAnywhere的Web请求有超时限制（免费账户通常为30秒），爬取10多个RSS源可能未完成就被中断，导致数据未写入数据库。建议将爬取逻辑改为后台任务（使用PythonAnywhere的Tasks功能），或减少单次爬取的RSS源数量，同时优化爬取速度（比如采用异步请求）。

内容的提问来源于stack exchange，提问作者elksie5000