如何在scrapy中使用CSS选择器从链接中获取href值？

from scrapy import Selector

def parse(self, response):
    # 使用CSS选择器获取包含链接的HTML元素
    link_elements = response.css('a')

def parse(self, response):
    link_elements = response.css('a')
    for link_element in link_elements:
        # 使用CSS选择器提取href值
        href = link_element.css('::attr(href)').get()

from scrapy import Selector

class MySpider(scrapy.Spider):
    name = 'my_spider'
    start_urls = ['http://example.com']

    def parse(self, response):
        link_elements = response.css('a')
        for link_element in link_elements:
            href = link_element.css('::attr(href)').get()
            yield {
                'href': href
            }