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# Python如何搭建爬虫程序
## 一、爬虫技术概述
网络爬虫(Web Crawler)是一种自动获取网页内容的程序,广泛应用于搜索引擎、数据分析和信息聚合等领域。Python凭借其丰富的库和简洁的语法,成为构建爬虫的首选语言之一。
### 核心组件
1. **HTTP请求库**:如`requests`、`urllib`
2. **HTML解析库**:如`BeautifulSoup`、`lxml`
3. **数据存储模块**:如`csv`、`sqlite3`
4. **并发处理**:如`asyncio`、`Scrapy`框架
---
## 二、基础爬虫搭建步骤
### 1. 环境准备
```python
pip install requests beautifulsoup4
import requests
url = "https://example.com"
headers = {"User-Agent": "Mozilla/5.0"}
response = requests.get(url, headers=headers)
print(response.status_code) # 200表示成功
print(response.text[:500]) # 打印前500字符
from bs4 import BeautifulSoup
soup = BeautifulSoup(response.text, 'html.parser')
titles = soup.find_all('h1')
for title in titles:
print(title.get_text())
import csv
with open('output.csv', 'w', newline='', encoding='utf-8') as f:
writer = csv.writer(f)
writer.writerow(['标题', '链接'])
for link in soup.find_all('a'):
writer.writerow([link.get_text(), link.get('href')])
使用selenium
模拟浏览器:
from selenium import webdriver
driver = webdriver.Chrome()
driver.get("https://dynamic-site.com")
dynamic_content = driver.page_source
import time
import random
time.sleep(random.uniform(1, 3))
创建项目:
pip install scrapy
scrapy startproject myproject
定义爬虫:
import scrapy
class MySpider(scrapy.Spider):
name = "example"
start_urls = ["https://example.com"]
def parse(self, response):
yield {
'title': response.css('h1::text').get(),
'url': response.url
}
/robots.txt
import requests
from bs4 import BeautifulSoup
import csv
import time
def simple_crawler():
url = "https://books.toscrape.com/"
headers = {"User-Agent": "Mozilla/5.0"}
try:
response = requests.get(url, headers=headers)
response.raise_for_status()
soup = BeautifulSoup(response.text, 'lxml')
books = soup.select('article.product_pod')
with open('books.csv', 'w', encoding='utf-8', newline='') as f:
writer = csv.writer(f)
writer.writerow(['Title', 'Price', 'Rating'])
for book in books:
title = book.h3.a['title']
price = book.select('p.price_color')[0].get_text()
rating = book.p['class'][1]
writer.writerow([title, price, rating])
print("数据抓取完成")
except Exception as e:
print(f"发生错误: {e}")
if __name__ == "__main__":
simple_crawler()
requests.get(url, verify=False) # 不推荐生产环境使用
response.encoding = 'gbk' # 或utf-8
session = requests.Session()
session.post(login_url, data={'user':'name', 'pass':'word'})
Python爬虫开发从简单到复杂有多种实现方式,建议:
1. 从基础requests+BeautifulSoup
开始
2. 逐步学习Scrapy等框架
3. 始终遵守法律法规
4. 定期关注反爬技术演变
提示:实际开发中建议添加异常处理、日志记录等功能增强健壮性。 “`
(全文约1100字)
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