为什么xpath的extract（）返回一个锚元素的href属性的空列表？

Question

Why do I get an empty list when trying to extract the href attribute of the anchor tag located on the following url: https://www.udemy.com/courses/search/?src=ukw&q=accounting using scrapy?

This is my code to extract the <a></a> element located inside the list-view-course-card--course-card-wrapper--TJ6ET class:

response.xpath("//div[@class='list-view-course-card--course-card-wrapper--TJ6ET']/a/@href").extract()

Answer 1

This site makes API calls to retrieve all the data. You can use the scrapy shell to see the response that the site is returning. scrapy shell 'https://www.udemy.com/courses/search/?src=ukw&q=accounting' and then view(response) .

The data you are looking for is available at the following api call : ' https://www.udemy.com/api-2.0/search-courses/?fields[locale]=simple_english_title&src=ukw&q=accounting ' . However, if you try to access this link directly, you will get a json object saying that you do not have permission to perform this action. How did I find this link ? Load the url on your browser, and go to the network tab on your developer tools and look for XHR objects.

The following spider will first make a request to the primary link and then make a request to the api call. You will have to parse the json object that was returned to obtain your data. If you want to scale this spider for more products, you might want to look for a pattern in the structure of the api call.

import scrapy

class UdemySpider(scrapy.Spider):

    name = 'udemy'
    newurl = 'https://www.udemy.com/api-2.0/search-courses/?fields[locale]=simple_english_title&src=ukw&q=accounting'

    def start_requests(self):
        urls = ['https://www.udemy.com/courses/search/?src=ukw&q=accounting'

        ]
        for url in urls:
            yield scrapy.Request(url=url, callback=self.api_call)

    def api_call(self, response):
        print("Working on second page")
        yield scrapy.Request(url=self.newurl, callback=self.parse)

    def parse(self, response):
        #code to parse json object
`