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Python
at develop
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from scrapy.http import Requestfrom scrapy import logfrom scrapy.selector import Selector
from source import Sourcefrom FourmiCrawler.items import Result
class WikipediaParser(Source): """ Wikipedia scraper for chemical properties
This parser parses Wikipedia info boxes (also bordered) to obtain properties and their values. It also returns requests with other external sources which contain information on parsed subject. """
website = "http://en\\.wikipedia\\.org/wiki/.*" __spider = None searched_compounds = []
def __init__(self, config=None): Source.__init__(self, config)
def parse(self, response): """ Distributes the above described behaviour :param response: The incoming search request :return: Returns the found properties if response is unique or returns none if it's already known """ log.msg('A response from %s just arrived!' % response.url, level=log.DEBUG) sel = Selector(response) compound = sel.xpath('//h1[@id="firstHeading"]//span/text()').extract()[0] # makes sure to use main page if compound in self.searched_compounds: return None else: items = self.parse_infobox(sel) self.searched_compounds.append(compound) return items
def parse_infobox(self, sel): """ Scrape data from infobox on wikipedia.
Data from two types of infoboxes: class="infobox bordered" and class="infobox" is scraped and :param sel: The selector with the html-information of the page to parse :return: item_list: Returns a list of properties with their values, source, etc.. """
items = []
# scrape the chembox (wikipedia template) items = self.parse_chembox(sel, items)
# scrape the drugbox (wikipedia template) items = self.parse_drugbox(sel, items)
items = filter(lambda a: a['value'] != '', items) # remove items with an empty value item_list = self.clean_items(items)
identifiers = self.get_identifiers(sel)
#add extra sources to scrape from as requests for i, identifier in enumerate(identifiers): request = None #discard internal wikipedia links if re.match('//en\.wikipedia', identifier): log.msg('Found link to Wikipedia, this is not something to scrape: %s' % identifier, level=log.WARNING) #fix links starting with '//www.' elif re.match('/{2}', identifier): identifier = re.sub("/{2}", "http://", identifier) request = Request(identifier) else: request = Request(identifier) log.msg('New identifier found, request: %s' % identifier, level=log.DEBUG) item_list.append(request)
return item_list
def parse_chembox(self, sel, items): """ Scrape data from chembox infobox on wikipedia.
:param sel: The selector with the html-information of the page to parse :param items: the list of items where the result have to be stored in :return: items: the list of items with the new found and stored items """ tr_list = sel.xpath('.//table[@class="infobox bordered"]//td[not(@colspan)]'). \ xpath('normalize-space(string())') prop_names = tr_list[::2] prop_values = tr_list[1::2] for i, prop_name in enumerate(prop_names): item = self.newresult( attribute=prop_name.extract().encode('utf-8'), value=prop_values[i].extract().encode('utf-8') ) items.append(item) log.msg('Wiki prop: |%s| |%s| |%s|' % (item['attribute'], item['value'], item['source']), level=log.DEBUG) return items
def parse_drugbox(self, sel, items): """ Scrape data from drugbox infobox on wikipedia.
:param sel: The selector with the html-information of the page to parse :param items: the list of items where the result have to be stored in :return: items: the list of items with the new found and stored items """ tr_list2 = sel.xpath('.//table[@class="infobox"]//tr') log.msg('dit: %s' % tr_list2, level=log.DEBUG) for tablerow in tr_list2: log.msg('item: %s' % tablerow.xpath('./th').xpath('normalize-space(string())'), level=log.DEBUG) if tablerow.xpath('./th').xpath('normalize-space(string())') and tablerow.xpath('./td').xpath( 'normalize-space(string())'): item = self.newresult( attribute=tablerow.xpath('./th').xpath('normalize-space(string())').extract()[0].encode('utf-8'), value=tablerow.xpath('./td').xpath('normalize-space(string())').extract()[0].encode('utf-8'), ) items.append(item) log.msg( 'Wiki prop: |attribute: %s| |value: %s| |%s|' % (item['attribute'], item['value'], item['source']), level=log.DEBUG) return items
def new_compound_request(self, compound): return Request(url=self.website[:-2].replace("\\", "") + compound, callback=self.parse)
@staticmethod def clean_items(items):
""" Clean up properties using regex, makes it possible to split the values from the units
Almost not in use, only cleans J/K/mol values and boiling/melting points.
:param items: List of properties with their values, source, etc.. :return: items: List of now cleaned up items """ for item in items: value = item['value'] m = re.search('F;\s(\d+[\.,]?\d*)', value) # clean up numerical Kelvin value (after F) if m: item['value'] = m.group(1) + " K" m = re.match('(\d+[\.,]?\d*)\sJ\sK.+mol', value) # clean up J/K/mol values if m: item['value'] = m.group(1) + " J/K/mol" return items
@staticmethod def get_identifiers(sel): """ Find external links, named 'Identifiers' to different sources.
:param sel: The selector with the html-information of the page to parse :return: links: New links which can be used to expand the crawlers search """ links = sel.xpath('//span[contains(concat(" ",normalize-space(@class)," "),"reflink")]/a' '[contains(concat(" ",normalize-space(@class)," "),"external")]/@href').extract() return links
def newresult(self, attribute, value): return Result( { 'attribute': attribute, 'value': value, 'source': 'Wikipedia', 'reliability': self.cfg['reliability'], 'conditions': '' })