117 lines
5.0 KiB
Python
117 lines
5.0 KiB
Python
from scrapy.http import Request
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from scrapy import log
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from source import Source
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from scrapy.selector import Selector
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from FourmiCrawler.items import Result
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import re
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class WikipediaParser(Source):
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""" Wikipedia scraper for chemical properties
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This parser parses Wikipedia info boxes (also bordered) to obtain properties and their values.
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It also returns requests with other external sources which contain information on parsed subject.
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"""
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website = "http://en.wikipedia.org/wiki/*"
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__spider = None
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searched_compounds = []
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def __init__(self):
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Source.__init__(self)
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def parse(self, response):
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""" Distributes the above described behaviour """
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log.msg('A response from %s just arrived!' % response.url, level=log.DEBUG)
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sel = Selector(response)
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compound = sel.xpath('//h1[@id="firstHeading"]//span/text()').extract()[0] # makes sure to use main page
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if compound in self.searched_compounds:
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return None
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else:
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items = self.parse_infobox(sel)
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self.searched_compounds.append(compound)
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return items
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def parse_infobox(self, sel):
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""" scrape data from infobox on wikipedia. """
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items = []
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#be sure to get chembox (wikipedia template)
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tr_list = sel.xpath('.//table[@class="infobox bordered"]//td[not(@colspan)]'). \
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xpath('normalize-space(string())')
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prop_names = tr_list[::2]
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prop_values = tr_list[1::2]
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for i, prop_name in enumerate(prop_names):
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item = Result({
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'attribute': prop_name.extract().encode('utf-8'),
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'value': prop_values[i].extract().encode('utf-8'),
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'source': "Wikipedia",
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'reliability': "Unknown",
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'conditions': ""
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})
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items.append(item)
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log.msg('Wiki prop: |%s| |%s| |%s|' % (item['attribute'], item['value'], item['source']), level=log.DEBUG)
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#scrape the drugbox (wikipedia template)
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tr_list2 = sel.xpath('.//table[@class="infobox"]//tr')
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log.msg('dit: %s' % tr_list2, level=log.DEBUG)
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for tablerow in tr_list2:
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log.msg('item: %s' % tablerow.xpath('./th').xpath('normalize-space(string())'), level=log.DEBUG)
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if tablerow.xpath('./th').xpath('normalize-space(string())') and tablerow.xpath('./td').xpath(
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'normalize-space(string())'):
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item = Result({
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'attribute': tablerow.xpath('./th').xpath('normalize-space(string())').extract()[0].encode('utf-8'),
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'value': tablerow.xpath('./td').xpath('normalize-space(string())').extract()[0].encode('utf-8'),
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'source': "Wikipedia",
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'reliability': "Unknown",
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'conditions': ""
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})
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items.append(item)
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log.msg(
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'Wiki prop: |attribute: %s| |value: %s| |%s|' % (item['attribute'], item['value'], item['source']),
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level=log.DEBUG)
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items = filter(lambda a: a['value'] != '', items) # remove items with an empty value
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item_list = self.clean_items(items)
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identifiers = self.get_identifiers(sel)
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#add extra sources to scrape from as requests
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for i, identifier in enumerate(identifiers):
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request = None
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#discard internal wikipedia links
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if re.match('//en\.wikipedia', identifier):
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log.msg('Found link to Wikipedia, this is not something to scrape: %s' % identifier, level=log.WARNING)
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#fix links starting with '//www.'
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elif re.match('/{2}', identifier):
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identifier = re.sub("/{2}", "http://", identifier)
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request = Request(identifier)
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else:
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request = Request(identifier)
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log.msg('New identifier found, request: %s' % identifier, level=log.DEBUG)
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item_list.append(request)
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return item_list
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def new_compound_request(self, compound):
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return Request(url=self.website[:-1] + compound, callback=self.parse)
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@staticmethod
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def clean_items(items):
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""" clean up properties using regex, makes it possible to split the values from the units """
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for item in items:
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value = item['value']
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m = re.search('F;\s(\d+[\.,]?\d*)', value) # clean up numerical Kelvin value (after F)
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if m:
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item['value'] = m.group(1) + " K"
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m = re.match('(\d+[\.,]?\d*)\sJ\sK.+mol', value) # clean up J/K/mol values
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if m:
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item['value'] = m.group(1) + " J/K/mol"
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return items
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@staticmethod
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def get_identifiers(sel):
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""" find external links, named 'Identifiers' to different sources. """
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links = sel.xpath('//span[contains(concat(" ",normalize-space(@class)," "),"reflink")]/a'
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'[contains(concat(" ",normalize-space(@class)," "),"external")]/@href').extract()
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return links |