1from scrapy.spiders import Spider
2from scrapy.utils.spider import iterate_spider_output
3
4
5class InitSpider(Spider):
6    """Base Spider with initialization facilities"""
7
8    def start_requests(self):
9        self._postinit_reqs = super().start_requests()
10        return iterate_spider_output(self.init_request())
11
12    def initialized(self, response=None):
13        """This method must be set as the callback of your last initialization
14        request. See self.init_request() docstring for more info.
15        """
16        return self.__dict__.pop('_postinit_reqs')
17
18    def init_request(self):
19        """This function should return one initialization request, with the
20        self.initialized method as callback. When the self.initialized method
21        is called this spider is considered initialized. If you need to perform
22        several requests for initializing your spider, you can do so by using
23        different callbacks. The only requirement is that the final callback
24        (of the last initialization request) must be self.initialized.
25
26        The default implementation calls self.initialized immediately, and
27        means that no initialization is needed. This method should be
28        overridden only when you need to perform requests to initialize your
29        spider
30        """
31        return self.initialized()
32