Conflicts When Generating Start Urls - scrapy

Question

I'm working on retrieving information from the National Gallery of Art's online catalog. Due to the catalog's structure, I can't navigate by extracting and following links from entry to entry. Fortunately, each object in the collection has a predictable url. I want my spider to navigate the collection by generating start urls.
I have attempted to solve my problem by implementing the solution from this thread. Unfortunately, this seems to break another part of my spider. The error log reveals that my urls are being successfully generated, but they aren't being processed correctly. If I'm interpreting the log correctly—which I suspect I'm not—there is a conflict between the redefinition of the start_urls that allows me to generate the urls I need and the rules section of the spider. As things stand now, the spider also doesn't respect the number of pages that I ask it to crawl.
You'll find my spider and a typical error below. I appreciate any help you can offer.
Spider:
URL = "http://www.nga.gov/content/ngaweb/Collection/art-object-page.%d"
starting_number = 1312
number_of_pages = 10
class NGASpider(CrawlSpider):
name = 'ngamedallions'
allowed_domains = ['nga.gov']
start_urls = [URL % starting_number]
rules = (
Rule(LinkExtractor(allow=('art-object-page.*','objects/*')),callback='parse_CatalogRecord',
follow=True))
def __init__(self):
self.page_number = starting_number
def start_requests(self):
for i in range (self.page_number, number_of_pages, -1):
yield Request(url = URL % i + ".html" , callback=self.parse)
def parse_CatalogRecord(self, response):
CatalogRecord = ItemLoader(item=NgamedallionsItem(), response=response)
CatalogRecord.default_output_processor = TakeFirst()
CatalogRecord.image_urls_out = scrapy.loader.processors.Identity()
keywords = "medal|medallion"
r = re.compile('.*(%s).*' % keywords, re.IGNORECASE|re.MULTILINE|re.UNICODE)
if r.search(response.body_as_unicode()):
CatalogRecord.add_xpath('title', './/dl[#class="artwork-details"]/dt[#class="title"]/text()')
CatalogRecord.add_xpath('accession', './/dd[#class="accession"]/text()')
CatalogRecord.add_xpath('inscription', './/div[#id="inscription"]/p/text()')
CatalogRecord.add_xpath('image_urls', './/img[#class="mainImg"]/#src')
return CatalogRecord.load_item()
Typical Error:
2016-04-29 15:35:00 [scrapy] ERROR: Spider error processing <GET http://www.nga.gov/content/ngaweb/Collection/art-object-page.1178.html> (referer: None)
Traceback (most recent call last):
File "/usr/lib/pymodules/python2.7/scrapy/utils/defer.py", line 102, in iter_errback
yield next(it)
File "/usr/lib/pymodules/python2.7/scrapy/spidermiddlewares/offsite.py", line 28, in process_spider_output
for x in result:
File "/usr/lib/pymodules/python2.7/scrapy/spidermiddlewares/referer.py", line 22, in <genexpr>
return (_set_referer(r) for r in result or ())
File "/usr/lib/pymodules/python2.7/scrapy/spidermiddlewares/urllength.py", line 37, in <genexpr>
return (r for r in result or () if _filter(r))
File "/usr/lib/pymodules/python2.7/scrapy/spidermiddlewares/depth.py", line 54, in <genexpr>
return (r for r in result or () if _filter(r))
File "/usr/lib/pymodules/python2.7/scrapy/spiders/crawl.py", line 73, in _parse_response
for request_or_item in self._requests_to_follow(response):
File "/usr/lib/pymodules/python2.7/scrapy/spiders/crawl.py", line 51, in _requests_to_follow
for n, rule in enumerate(self._rules):
AttributeError: 'NGASpider' object has no attribute '_rules'
Update in Resonse to eLRuLL's Solution
Simply removing def __init__ and start_urls allows my spider to crawl my generated urls. However, it also seems to prevent 'def parse_CatalogRecord(self, response)' from being applied. When I run the spider now, it only scrapes pages from outside the range of generated urls. My revised spider and log output follow below.
Spider:
URL = "http://www.nga.gov/content/ngaweb/Collection/art-object-page.%d"
starting_number = 1312
number_of_pages = 1311
class NGASpider(CrawlSpider):
name = 'ngamedallions'
allowed_domains = ['nga.gov']
rules = (
Rule(LinkExtractor(allow=('art-object-page.*','objects/*')),callback='parse_CatalogRecord',
follow=True))
def start_requests(self):
self.page_number = starting_number
for i in range (self.page_number, number_of_pages, -1):
yield Request(url = URL % i + ".html" , callback=self.parse)
def parse_CatalogRecord(self, response):
CatalogRecord = ItemLoader(item=NgamedallionsItem(), response=response)
CatalogRecord.default_output_processor = TakeFirst()
CatalogRecord.image_urls_out = scrapy.loader.processors.Identity()
keywords = "medal|medallion"
r = re.compile('.*(%s).*' % keywords, re.IGNORECASE|re.MULTILINE|re.UNICODE)
if r.search(response.body_as_unicode()):
CatalogRecord.add_xpath('title', './/dl[#class="artwork-details"]/dt[#class="title"]/text()')
CatalogRecord.add_xpath('accession', './/dd[#class="accession"]/text()')
CatalogRecord.add_xpath('inscription', './/div[#id="inscription"]/p/text()')
CatalogRecord.add_xpath('image_urls', './/img[#class="mainImg"]/#src')
return CatalogRecord.load_item()
Log:
2016-05-02 15:50:02 [scrapy] INFO: Scrapy 1.0.5.post4+g4b324a8 started (bot: ngamedallions)
2016-05-02 15:50:02 [scrapy] INFO: Optional features available: ssl, http11
2016-05-02 15:50:02 [scrapy] INFO: Overridden settings: {'NEWSPIDER_MODULE': 'ngamedallions.spiders', 'FEED_URI': 'items.json', 'SPIDER_MODULES': ['ngamedallions.spiders'], 'BOT_NAME': 'ngamedallions', 'FEED_FORMAT': 'json', 'DOWNLOAD_DELAY': 3}
2016-05-02 15:50:02 [scrapy] INFO: Enabled extensions: CloseSpider, FeedExporter, TelnetConsole, LogStats, CoreStats, SpiderState
2016-05-02 15:50:02 [scrapy] INFO: Enabled downloader middlewares: HttpAuthMiddleware, DownloadTimeoutMiddleware, UserAgentMiddleware, RetryMiddleware, DefaultHeadersMiddleware, MetaRefreshMiddleware, HttpCompressionMiddleware, RedirectMiddleware, CookiesMiddleware, ChunkedTransferMiddleware, DownloaderStats
2016-05-02 15:50:02 [scrapy] INFO: Enabled spider middlewares: HttpErrorMiddleware, OffsiteMiddleware, RefererMiddleware, UrlLengthMiddleware, DepthMiddleware
2016-05-02 15:50:02 [scrapy] INFO: Enabled item pipelines: ImagesPipeline
2016-05-02 15:50:02 [scrapy] INFO: Spider opened
2016-05-02 15:50:02 [scrapy] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2016-05-02 15:50:02 [scrapy] DEBUG: Telnet console listening on 127.0.0.1:6023
2016-05-02 15:50:02 [scrapy] DEBUG: Crawled (200) <GET http://www.nga.gov/content/ngaweb/Collection/art-object-page.1312.html> (referer: None)
2016-05-02 15:50:02 [scrapy] DEBUG: Filtered duplicate request: <GET http://www.nga.gov/content/ngaweb/Collection/art-object-page.1312.html> - no more duplicates will be shown (see DUPEFILTER_DEBUG to show all duplicates)
2016-05-02 15:50:05 [scrapy] DEBUG: Crawled (200) <GET http://www.nga.gov/content/ngaweb/Collection/art-object-page.1313.html> (referer: http://www.nga.gov/content/ngaweb/Collection/art-object-page.1312.html)
2016-05-02 15:50:05 [scrapy] DEBUG: File (uptodate): Downloaded image from <GET http://media.nga.gov/public/objects/1/3/1/3/1313-primary-0-440x400.jpg> referred in <None>
2016-05-02 15:50:05 [scrapy] DEBUG: Scraped from <200 http://www.nga.gov/content/ngaweb/Collection/art-object-page.1313.html>
{'accession': u'1942.9.163.b',
'image_urls': [u'http://media.nga.gov/public/objects/1/3/1/3/1313-primary-0-440x400.jpg'],
'images': [{'checksum': '9d5f2e30230aeec1582ca087bcde6bfa',
'path': 'full/3a692347183d26ffefe9ba0af80b0b6bf247fae5.jpg',
'url': 'http://media.nga.gov/public/objects/1/3/1/3/1313-primary-0-440x400.jpg'}],
'inscription': u'around top circumference: TRINACRIA IANI; upper center: PELORVS ; across center: PA LI; across bottom: BELAVRA',
'title': u'House between Two Hills [reverse]'}
2016-05-02 15:50:05 [scrapy] INFO: Closing spider (finished)
2016-05-02 15:50:05 [scrapy] INFO: Stored json feed (1 items) in: items.json
2016-05-02 15:50:05 [scrapy] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 631,
'downloader/request_count': 2,
'downloader/request_method_count/GET': 2,
'downloader/response_bytes': 26324,
'downloader/response_count': 2,
'downloader/response_status_count/200': 2,
'dupefilter/filtered': 3,
'file_count': 1,
'file_status_count/uptodate': 1,
'finish_reason': 'finished',
'finish_time': datetime.datetime(2016, 5, 2, 19, 50, 5, 810570),
'item_scraped_count': 1,
'log_count/DEBUG': 6,
'log_count/INFO': 8,
'request_depth_max': 2,
'response_received_count': 2,
'scheduler/dequeued': 2,
'scheduler/dequeued/memory': 2,
'scheduler/enqueued': 2,
'scheduler/enqueued/memory': 2,
'start_time': datetime.datetime(2016, 5, 2, 19, 50, 2, 455508)}
2016-05-02 15:50:05 [scrapy] INFO: Spider closed (finished)

Answer 1

don't override the __init__ method if you are not going to call super.
Now, you don't really need to declare start_urls for your spider to work if you are going to use start_requests.
Just remove your def __init__ method and no need for start_urls to exist.
UPDATE
Ok my mistake, looks like CrawlSpider needs the start_urls attribute, so just create it instead of using the start_requests method:
start_urls = [URL % i + '.html' for i in range (starting_number, number_of_pages, -1)]
and remove start_requests