Scrapy's pagination error - pagination

Question

Hi guys I'm getting the following pagination error while tying to scrape a website
2017-07-27 18:30:21 [scrapy.core.scraper] ERROR: Spider error processing <GET https://www.pedidosja.com.br/restaurantes/sao-paulo?a=rua%20tenente%20negr%C3%A3o%20200&cep=04530030&doorNumber=200&bairro=Itaim%20Bibi&lat=-23.585202&lng=-46.671715199999994> (referer: None)
Traceback (most recent call last):
File "/usr/local/lib/python3.5/dist-packages/scrapy/utils/defer.py", line 102, in iter_errback
yield next(it)
File "/usr/local/lib/python3.5/dist-packages/scrapy/spidermiddlewares/offsite.py", line 29, in process_spider_output
for x in result:
File "/usr/local/lib/python3.5/dist-packages/scrapy/spidermiddlewares/referer.py", line 339, in <genexpr>
return (_set_referer(r) for r in result or ())
File "/usr/local/lib/python3.5/dist-packages/scrapy/spidermiddlewares/urllength.py", line 37, in <genexpr>
return (r for r in result or () if _filter(r))
File "/usr/local/lib/python3.5/dist-packages/scrapy/spidermiddlewares/depth.py", line 58, in <genexpr>
return (r for r in result or () if _filter(r))
File "/root/Documents/Spiders/pedidosYa/pedidosYa/spiders/pedidosya.py", line 35, in parse
next_page_url = response.urljoin(next_page_url)
File "/usr/local/lib/python3.5/dist-packages/scrapy/http/response/text.py", line 82, in urljoin
return urljoin(get_base_url(self), url)
File "/usr/lib/python3.5/urllib/parse.py", line 416, in urljoin
base, url, _coerce_result = _coerce_args(base, url)
File "/usr/lib/python3.5/urllib/parse.py", line 112, in _coerce_args
raise TypeError("Cannot mix str and non-str arguments")
TypeError: Cannot mix str and non-str arguments
2017-07-27 18:30:21 [scrapy.core.engine] INFO: Closing spider (finished)
2017-07-27 18:30:21 [scrapy.extensions.feedexport] INFO: Stored csv feed (13 items) in: test3.csv
2017-07-27 18:30:21 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 653,
'downloader/request_count': 2,
'downloader/request_method_count/GET': 2,
'downloader/response_bytes': 62571,
'downloader/response_count': 2,
'downloader/response_status_count/200': 2,
'finish_reason': 'finished',
'finish_time': datetime.datetime(2017, 7, 27, 23, 30, 21, 221038),
'item_scraped_count': 13,
'log_count/DEBUG': 16,
'log_count/ERROR': 1,
'log_count/INFO': 8,
'memusage/max': 49278976,
'memusage/startup': 49278976,
'response_received_count': 2,
'scheduler/dequeued': 1,
'scheduler/dequeued/memory': 1,
'scheduler/enqueued': 1,
'scheduler/enqueued/memory': 1,
'spider_exceptions/TypeError': 1,
'start_time': datetime.datetime(2017, 7, 27, 23, 30, 17, 538310)}
2017-07-27 18:30:21 [scrapy.core.engine] INFO: Spider closed (finished)
The spider is raising a type error "Cannot mix str and non-str arguments" I not very experienced in pyhton, I would also apreciate some
resources where I could learn about this type of error. Bellow you will find the code of the spider.
# -*- coding: utf-8 -*-
import scrapy
from pedidosYa.items import PedidosyaItem
from scrapy.loader import ItemLoader
from scrapy.loader.processors import MapCompose
class PedidosyaSpider(scrapy.Spider):
name = 'pedidosya'
allowed_domains = ['www.pedidosya.com.br']
start_urls = [
'https://www.pedidosja.com.br/restaurantes/sao-paulo?a=rua%20tenente%20negr%C3%A3o%20200&cep=04530030&doorNumber=200&bairro=Itaim%20Bibi&lat=-23.585202&lng=-46.671715199999994']
def parse(self, response):
# need to define wrapper
for wrapper in response.css('.restaurant-wrapper.peyaCard.show.with_tags'):
l = ItemLoader(item=PedidosyaItem(), selector=wrapper)
l.add_css('Name', 'a.arrivalName::text')
l.add_css('Menu1', 'span.categories > span::text', MapCompose(str.strip))
l.add_css('Menu2', 'span.categories > span + span::text', MapCompose(str.strip))
l.add_css('Menu3', 'span.categories > span + span + span::text', MapCompose(str.strip))
l.add_css('Address', 'span.address::text', MapCompose(str.strip))
l.add_css('DeliveryTime', 'i.delTime::text', MapCompose(str.strip))
l.add_css('CreditCard', 'ul.content_credit_cards > li > img::attr(alt)', MapCompose(str.strip))
l.add_css('DeliveryCost', 'div.shipping > i::text', MapCompose(str.strip))
l.add_css('Rankink', 'span.ranking i::text', MapCompose(str.strip))
l.add_css('No', 'span.ranking a::text', MapCompose(str.strip))
l.add_css('Sponsor', 'span.grey_small.not-logged::text', MapCompose(str.strip))
l.add_css('DeliveryMinimun', 'div.minDelivery::text', MapCompose(str.strip))
l.add_css('Distance', 'div.distance i::text', MapCompose(str.strip))
yield l.load_item()
next_page_url = response.css('li.arrow.next > a ::attr(href)').extract()
if next_page_url:
next_page_url = response.urljoin(next_page_url)
yield scrapy.Request(url=next_page_url, callback=self.parse)
Thank you in advance and have a wonderfull day!!

Answer 1

next_page_url = response.css('li.arrow.next > a ::attr(href)').extract()
^^^^^^^^^^
if next_page_url:
next_page_url = response.urljoin(next_page_url)
^^^^^^^^^^^^^
Here you are calling urljoin on a list since extract() method when creating next_page_url returns a list of all values, even if it's only one member.
To remedy this use extract_first() instead:
next_page_url = response.css('li.arrow.next > a ::attr(href)').extract_first()
^^^^^^^^^^^^^^^

Answer 2

The problem is in this line:
next_page_url = response.css('li.arrow.next > a::attr(href)').extract()
because extract() method returns always a list of results, even if it founds just one. Either use extract_first() method which will give you just the first result:
next_page_url = response.css('li.arrow.next > a::attr(href)').extract_first()
or get the first element of the results list yourself:
next_page_url = response.css('li.arrow.next > a::attr(href)').extract()[0]