python爬虫如何写，有哪些成功爬取的案例

编写Python爬虫时，常用的库包括Requests、Beautiful Soup和Scrapy。以下是三个简单的Python爬虫案例，分别使用Requests和Beautiful Soup，以及Scrapy。

1. 使用Requests和Beautiful Soup爬取网页内容：

import requests
from bs4 import BeautifulSoupurl = "https://example.com"
response = requests.get(url)if response.status_code == 200:soup = BeautifulSoup(response.text, 'html.parser')# 在这里可以使用Beautiful Soup提取页面内容# 例如：titles = soup.find_all('h2')print(soup.title.text)
else:print(f"Failed to retrieve the page. Status code: {response.status_code}")

2. 使用Requests和正则表达式爬取图片：

import requests
import re
from urllib.parse import urljoinurl = "https://example.com"
response = requests.get(url)if response.status_code == 200:image_urls = re.findall(r'<img.*?src=["\'](.*?)["\']', response.text)for img_url in image_urls:full_url = urljoin(url, img_url)# 在这里可以下载图片或进行其他处理# 例如：response = requests.get(full_url); save_image(response.content, "image.jpg")print(full_url)
else:print(f"Failed to retrieve the page. Status code: {response.status_code}")

3. 使用Scrapy爬取网站：

首先，确保已安装Scrapy：

pip install scrapy

创建一个新的Scrapy项目：

scrapy startproject myproject
cd myproject

编辑Spider：

# myproject/spiders/myspider.py
import scrapyclass MySpider(scrapy.Spider):name = 'myspider'start_urls = ['https://example.com']def parse(self, response):# 在这里可以使用XPath或CSS选择器提取数据# 例如：titles = response.xpath('//h2/text()').getall()title = response.css('title::text').get()print(title)