Scrapy can't get data when following links - xpath

Question

I have asked a question like this Scrapy can't get data. But I have a new problem when using another spider. I've pay attention to the xpath, but it seems like there is an same error in this program.
Here is my spider's code:
from scrapy.contrib.spiders import CrawlSpider, Rule
from scrapy.selector import Selector
from scrapy import Item, Field
from scrapy.contrib.spiders import CrawlSpider, Rule
from scrapy.contrib.linkextractors.sgml import SgmlLinkExtractor
from DB_Connection import DB_Con
class UniParc(Item):
database = Field()
identifier = Field()
version = Field()
organism = Field()
first_seen = Field()
last_seen = Field()
active = Field()
source = Field()
class UniParcSpider(CrawlSpider):
name = "UniParc"
allowed_domains = ["uniprot.org"]
start_urls = ["http://www.uniprot.org/uniparc/?query=rna&offset=25&sort=score&columns=id%2corganisms%2ckb%2cfirst-seen%2clast-seen%2clength"]
rules = (
Rule(SgmlLinkExtractor(allow=(), restrict_xpaths=('//*[#id="results"]/tr/td[2]/a',)), callback="parse_items", follow = True),
)
def parse_items(self, response):
hxs = Selector(response)
sites = hxs.xpath('//*[#id="results"]/tr')
db = DB_Con()
collection = db.getcollection(self.term)
for site in sites:
item = UniParc()
item["database"] = map(unicode.strip, site.xpath("td[1]/text()").extract())
item["identifier"] = map(unicode.strip, site.xpath("td[2]/a/text()").extract())
item["version"] = map(unicode.strip, site.xpath("td[3]/text()").extract())
item["organism"] = map(unicode.strip, site.xpath("td[4]/a/text()").extract())
item["first_seen"] = map(unicode.strip, site.xpath("td[5]/text()").extract())
item["last_seen"] = map(unicode.strip, site.xpath("td[6]/text()").extract())
item["active"] = map(unicode.strip, site.xpath("td[7]/text()").extract())
item['source'] = self.name
collection.update({"identifier": item['identifier']}, dict(item), upsert=True)
yield item
I used rules to extract the link which I want to follow and get data from it. But it seems like no urls have been got from the start_url.
Here is the log:
2016-05-28 22:28:54 [scrapy] INFO: Enabled item pipelines:
2016-05-28 22:28:54 [scrapy] INFO: Spider opened
2016-05-28 22:28:54 [scrapy] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2016-05-28 22:28:54 [scrapy] DEBUG: Telnet console listening on 127.0.0.1:6023
2016-05-28 22:28:55 [scrapy] DEBUG: Crawled (200) <GET http://www.uniprot.org/uniparc/?query=rna&offset=25&sort=score&columns=id%2corganisms%2ckb%2cfirst-seen%2clast-seen%2clength> (referer: None)
2016-05-28 22:28:55 [scrapy] INFO: Closing spider (finished)
2016-05-28 22:28:55 [scrapy] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 314,
'downloader/request_count': 1,
'downloader/request_method_count/GET': 1,
'downloader/response_bytes': 12263,
'downloader/response_count': 1,
'downloader/response_status_count/200': 1,
'finish_reason': 'finished',
'finish_time': datetime.datetime(2016, 5, 28, 14, 28, 55, 638618),
'log_count/DEBUG': 2,
'log_count/INFO': 7,
'response_received_count': 1,
'scheduler/dequeued': 1,
'scheduler/dequeued/memory': 1,
'scheduler/enqueued': 1,
'scheduler/enqueued/memory': 1,
'start_time': datetime.datetime(2016, 5, 28, 14, 28, 54, 645490)}
So can anybody tell what's wrong with my code? Is there something wrong with my xpath? But I've check this so many times.

Answer 1

In order to fix the following the links step, just fix the XPath expression, replace:
//*[#id="results"]/tr/td[2]/a
with:
//*[#id="results"]//tr/td[2]/a
And, as a side note, you should not be inserting the extracted items into the database directly in the spider. For that, Scrapy offers the pipelines. In case of MongoDB, check out scrapy-mongodb. Also see:
Web Scraping With Scrapy and MongoDB