AttributeError: 'NoneType' object has no attribute 'random'

这个错误通常表示你在尝试对一个空值（NoneType）进行字符串分割操作。你需要确保你的代码能够处理空值的情况。比如，你可以添加一个判断语句来检查变量是否为空，然后再进行字符串分割操作。例如： ``` if my_string is not None: my_list = my_string.split(',') else: # 处理空值情况的代码 ``` 另外，你也可以在变量声明时给予一个默认值，以确保变量不会为空。例如： ``` my_string = some_function() my_list = my_string.split(',') if my_string is not None else [] ```

### 豆瓣图书评论爬虫 'NoneType' object has no attribute 'a' 错误解决方案 在爬取豆瓣图书评论时，出现 `'NoneType' object has no attribute 'a'` 的错误通常是因为目标页面中的某些 HTML 元素未能成功获取到，而后续代码尝试对该 `None` 对象调用了 `.find()` 或其他属性访问操作。以下是可能的原因以及对应的解决方案： #### 1. **反爬机制** 豆瓣网站具有较强的反爬策略，可能会检测并拒绝来自自动化工具的请求。如果未设置合适的请求头 (`headers`)，服务器会返回空白或异常响应内容，导致解析失败。 解决方法是在发起 HTTP 请求时加入自定义头部信息来模拟真实浏览器行为[^2]： ```python import requests from bs4 import BeautifulSoup fake_headers = { 'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36' } url = "https://book.douban.com/subject/{book_id}/comments/" response = requests.get(url, headers=fake_headers) if response.status_code != 200: raise Exception(f"Failed to fetch the page with status code {response.status_code}") soup = BeautifulSoup(response.text, 'html.parser') ``` #### 2. **HTML 结构变化** 目标网页的结构可能发生改变，或者部分书籍缺少评论链接，这可能导致 `.find('a')` 返回 `None` 值。 建议在执行 `.find()` 方法前增加判断逻辑以避免直接处理 `None` 类型对象[^1]: ```python comment_section = soup.find('div', class_='comment-item') if comment_section is not None: link_tag = comment_section.find('a') if link_tag is not None and hasattr(link_tag, 'href'): comment_url = link_tag['href'] else: print("No comments found or structure mismatch.") ``` #### 3. **网络连接不稳定** 偶尔由于网络波动或其他原因造成的数据传输不完全也可能引发此类问题。可以考虑重试机制提升稳定性[^3]: ```python def get_page_content(url, max_retries=3): attempt = 0 while attempt < max_retries: try: resp = requests.get(url, headers=fake_headers, timeout=10) if resp.status_code == 200: return resp.text except requests.RequestException as e: print(f"Request failed ({e}), retrying...") finally: attempt += 1 return None ``` 通过以上调整能够有效减少因外部因素引起的错误发生率。 --- ### 示例代码综合应用 下面给出一段完整的示例代码用于抓取豆瓣某本书籍下的用户评论列表，并妥善处理可能出现的各种情况: ```python import requests from bs4 import BeautifulSoup class DoubanBookCrawler: def __init__(self): self.headers = {'User-Agent': 'Your User Agent String'} def fetch_comments(self, book_id): base_url = f"https://book.douban.com/subject/{book_id}/comments" html_content = self._get_html(base_url) if not html_content: print("Unable to retrieve webpage content.") return [] parsed_data = [] soup = BeautifulSoup(html_content, 'lxml') items = soup.select('.comment-item') for item in items: user_info = item.find('span', attrs={'class':'comment-info'}) if user_info is None: continue username_element = user_info.a if username_element is None: continue username = username_element.string.strip() rating = user_info.span["title"] if user_info.span else "" date_posted = user_info.contents[-1].strip() review_text_div = item.find('p', attrs={'class':''}) review_text = review_text_div.text.strip() if review_text_div else "" parsed_data.append({ "username": username, "rating": rating, "date": date_posted, "review": review_text }) return parsed_data def _get_html(self, url, retries_left=3): try: res = requests.get(url, headers=self.headers, timeout=(3, 10)) if res.ok: return res.text elif retries_left > 0: time.sleep(2**retries_left + random.uniform(-0.5, 0.5)) # Exponential backoff strategy. return self._get_html(url, retries_left=retries_left-1) except Exception as ex: logging.error(str(ex)) crawler_instance = DoubanBookCrawler() reviews = crawler_instance.fetch_comments(book_id='example_book_id_here') for rvw in reviews[:5]: print(rvw) ``` ---