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Python 第二阶段 - 爬虫入门

🎯 今日目标

• 学会使用 BeautifulSoup 解析 HTML 网页内容
• 掌握常用的标签选择器与属性提取方法
• 为爬虫后续提取结构化数据打好基础

📘 学习内容详解

1. 📦 安装 BeautifulSoup 相关库

   pip install beautifulsoup4
   pip install lxml
   

   lxml 是解析器，速度快；也可使用 html.parser（Python 自带）。

2. 🍜 基本用法

   from bs4 import BeautifulSoup
   import requestsurl = "https://example.com"
   html = requests.get(url).textsoup = BeautifulSoup(html, 'lxml')  # 也可换成 'html.parser'
   

3. 🔍 常用标签查找方法

操作	示例	说明
获取标题内容	soup.title.text	获取
获取第一个标签	soup.p	第一个 <p> 标签
获取所有某类标签	soup.find_all(“p”)	返回列表
查找指定 class 的标签	soup.find_all(class_=“info”)	注意 class 是关键字
根据 id 查找标签	soup.find(id=“main”)
选择 CSS 选择器	soup.select(“div > p.info”)	返回列表

4. 🧲 获取属性和文本

   tag = soup.find("a")
   print(tag['href'])      # 获取属性
   print(tag.get('href'))  # 同上
   print(tag.text)         # 获取文本内容
   

💡 今日练习任务

1.用 requests 抓取网页 https://quotes.toscrape.com/
2. 用 BeautifulSoup 完成以下任务：

• 提取所有名人名言内容（位于 ）
• 提取作者名字（）
• 提取每条名言的标签（class=“tag”）

3. 把每条名言信息输出为字典：

   {"quote": "...","author": "...","tags": ["tag1", "tag2"]
   }
   

   练习脚本：

   # quotes_scraper.pyimport requests
   from bs4 import BeautifulSoupdef fetch_quotes():url = "https://quotes.toscrape.com/"headers = {'User-Agent': 'Mozilla/5.0'}response = requests.get(url, headers=headers)if response.status_code != 200:print(f"请求失败，状态码：{response.status_code}")returnsoup = BeautifulSoup(response.text, "lxml")# 查找所有名言块quote_blocks = soup.find_all("div", class_="quote")quotes_data = []for block in quote_blocks:quote_text = block.find("span", class_="text").text.strip()author = block.find("small", class_="author").text.strip()tags = [tag.text.strip() for tag in block.find_all("a", class_="tag")]quotes_data.append({"quote": quote_text,"author": author,"tags": tags})return quotes_dataif __name__ == "__main__":data = fetch_quotes()for i, quote in enumerate(data, start=1):print(f"\n第 {i} 条名言：")print(f"内容：{quote['quote']}")print(f"作者：{quote['author']}")print(f"标签：{', '.join(quote['tags'])}")
   

   输出结果为：

   第 1 条名言：
   内容：“The world as we have created it is a process of our thinking. It cannot be changed without changing our thinking.”
   作者：Albert Einstein
   标签：change, deep-thoughts, thinking, world第 2 条名言：
   内容：“It is our choices, Harry, that show what we truly are, far more than our abilities.”
   作者：J.K. Rowling
   标签：abilities, choices第 3 条名言：
   内容：“There are only two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle.”
   作者：Albert Einstein
   标签：inspirational, life, live, miracle, miracles第 4 条名言：
   内容：“The person, be it gentleman or lady, who has not pleasure in a good novel, must be intolerably stupid.”
   作者：Jane Austen
   标签：aliteracy, books, classic, humor第 5 条名言：
   内容：“Imperfection is beauty, madness is genius and it's better to be absolutely ridiculous than absolutely boring.”
   作者：Marilyn Monroe
   标签：be-yourself, inspirational第 6 条名言：
   内容：“Try not to become a man of success. Rather become a man of value.”
   作者：Albert Einstein
   标签：adulthood, success, value第 7 条名言：
   内容：“It is better to be hated for what you are than to be loved for what you are not.”
   作者：André Gide
   标签：life, love第 8 条名言：
   内容：“I have not failed. I've just found 10,000 ways that won't work.”
   作者：Thomas A. Edison
   标签：edison, failure, inspirational, paraphrased第 9 条名言：
   内容：“A woman is like a tea bag; you never know how strong it is until it's in hot water.”
   作者：Eleanor Roosevelt
   标签：misattributed-eleanor-roosevelt第 10 条名言：
   内容：“A day without sunshine is like, you know, night.”
   作者：Steve Martin
   标签：humor, obvious, simile
   

📎 小贴士

• 遇到复杂页面，建议先用浏览器 F12 检查结构。
• 尝试结合 select() 使用 CSS 选择器：soup.select(‘.quote span.text’)

📝 今日总结

• 初步掌握了 BeautifulSoup 的解析方式和用法
• 能提取文本、属性、class、id 等元素内容
• 可初步实现“结构化数据提取”，为爬虫数据存储铺路