def start_crawling(self,seed_pages,depth):
        """ User calls this function to start crawling the web """
        d = {}
        self.link_dict.clear()
       
        # initialize global dictionary variable to the seed page url's passed in
        for page in seed_pages:           
            self.link_dict[page] = self.PageInfo()
            d[page] = self.PageInfo()
        self.initial_depth = depth
        # start a recursive crawl
        # can't pass in self.link_dict because then i get a RuntimeError: dictionary changed size during iteration
        self.save_all_links_recursive(d,depth)
 User calls this function to start crawling the web 
recipes/Python/578060_A_Simple_Webcrawler/recipe-578060.py