How to make "tri-directional" scraping? - python-3.x

Question

I want to scrape a business directory with Scrapy and Python 3.
You know the concept of "bi-directional" scraping:
1st direction => Scraping the urls of details page of item (detail page of Business A, detail page of business B, etc....) which are displayed on 1 page of result.
2nd direction => Scraping the urls of pagination of resuls pages (page 1, page 2, page 3, etc...)
I guess you understand this stuff.
The website business directory I want to scrape has a 3rd "direction". All the businesses I want to scrape in this website are organised by ALPHABET.
I need to click on an ALPHABET letter to get thousands of businesses displayed on several pages pagination (please see pictures attached for better understanding).
So I added the alphabet urls by hand in the start_urls. But it didn't work. Have a look at my code:
class AnnuaireEntreprisesSpider(scrapy.Spider):
name = 'example'
allowed_domains = ['example.com']
#here I added the list of ALPHABET pages which containes several pages of results per letter
start_urls = ['http://www.example.com/entreprises-0-9.html',
'http://www.example.com/entreprises-a.html',
'http://www.example.com/entreprises-b.html',
'http://www.example.com/entreprises-c.html',
'http://www.example.com/entreprises-d.html',
'http://www.example.com/entreprises-e.html',
'http://www.example.com/entreprises-f.html',
'http://www.example.com/entreprises-g.html',
'http://www.example.com/entreprises-h.html',
'http://www.example.com/entreprises-i.html',
'http://www.example.com/entreprises-j.html',
'http://www.example.com/entreprises-k.html',
'http://www.example.com/entreprises-l.html',
'http://www.example.com/entreprises-m.html',
'http://www.example.com/entreprises-n.html',
'http://www.example.com/entreprises-o.html',
'http://www.example.com/entreprises-p.html',
'http://www.example.com/entreprises-q.html',
'http://www.example.com/entreprises-r.html',
'http://www.example.com/entreprises-s.html',
'http://www.example.com/entreprises-t.html',
'http://www.example.com/entreprises-u.html',
'http://www.example.com/entreprises-v.html',
'http://www.example.com/entreprises-w.html',
'http://www.example.com/entreprises-x.html',
'http://www.example.com/entreprises-y.html',
'http://www.example.com/entreprises-z.html'
]
def parse(self, response):
urls = response.xpath("//a[#class='btn-fiche dcL ']/#href").extract()
for url in urls:
#here I scrape the urls of detail page of business
absolute_url = response.urljoin(url)
print('Voici absolute url :' + absolute_url)
yield Request(absolute_url, callback=self.parse_startup)
next_page = response.xpath("//a[#class='nextPages']/#href").get() or ''
if next_page:
#Here I scrape the pagination urls
absolute_next_page = response.urljoin(next_page)
print('Voici absolute url NEXT PAGE :' + absolute_next_page)
yield response.follow(next_page, callback=self.parse)
def parse_startup(self, response):
print("Parse_startup details!!!")
#and here I scrape the details of the business
I am a beginner who started to learn Scrapy a few weeks ago.