在python中尝试使用BeautifulSoup抓取任何数据时，为什么我总是得到无列表或空列表

import requests
from bs4 import BeautifulSoup

headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3'}
response = requests.get('http://example.com', headers=headers)
soup = BeautifulSoup(response.text, 'html.parser')

# 示例：使用CSS选择器
items = soup.select('.item-class')
# 示例：使用XPath
from lxml import etree
items = soup.xpath('//div[@class="item-class"]')

import requests
from bs4 import BeautifulSoup

headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3'}

try:
    response = requests.get('http://example.com', headers=headers)
    response.raise_for_status()  # 检查请求是否成功
    soup = BeautifulSoup(response.text, 'html.parser')
    items = soup.select('.item-class')  # 替换为实际的选择器

    if not items:
        print("未找到匹配的数据")
    else:
        for item in items:
            print(item.text)
except requests.RequestException as e:
    print(f"请求错误: {e}")