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Web scraping 1 2-3 with python + scrapy (Summer BarCampHK 2012 version)


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Web scraping 1 2-3 with python + scrapy (Summer BarCampHK 2012 version)

  1. 1. Web Scraping 1-2-3 with Python + Scrapy Sammy Fung,
  2. 2. Today Agenda● Some Cases● Python and Scrapy
  3. 3. Web Scraping● a computer software technique of extracting information from websites. (Wikipedia)● for business, hobbies, research.......● NOT talk about business cases today.
  4. 4. CableTV & NOWTV Programme(Past)● 2004.● slow, slow, slow, or worst - cant connect.● use Flash.
  5. 5. HK Observatory and Joint TyphoonWarning Center● no easy data exchange format, eg. RSS/Atom.● We wont check websites everyday.
  6. 6. Transportation - KMB, PTES● no map view on KMB website for a bus route in the past.● Exteremly Poor, Ugly (or much worse) map UI on PTES.
  7. 7. My experiences on web scraping● 2004: php● year after: python● recent year: python with scrapy
  8. 8. Document Types● HTML, XML,......● Text● Others, eg. pictures, videos,......
  9. 9. Web Scraping● Look for right URLs to scrap.● Look for right content from webpages.● Saving data into data store.● When to run the web scraping program ?
  10. 10. What is Scrapy ?● An open source web scraping framework for Python.● Scrapy is a fast high-level screen scraping and web crawling framework, used to crawl websites and extract structured data from their pages. It can be used for a wide range of purposes, from data mining to monitoring and automated testing.
  11. 11. Features of Scrapy● define data you want to scrapy● write spider to extract data● Built-in: selecting and extracting data from HTML and XML● Built-in: JSON, CSV, XML output● Interactive shell console● Built-in: web service, telnet console, logging● Others
  12. 12. Installation of Scrapy● pip● APT repo● RPM● tarball (binary/source)
  13. 13. Create new scrapy project$ scrapy startproject mybotmybot/mybot/scrapy.cfgmybot/mybot/items.pymybot/mybot/pipeline.pymybot/mybot/settings.pymybot/mybot/spiders/myspider.pyetc.......
  14. 14. items.pyfrom scrapy.item import Item, Fieldclass HKOCurrentItem(Item): time = Field() station = Field() temperature = Field() humidity = Field() #......
  15. 15. spiders/ (1/5)from scrapy.spider import BaseSpiderfrom scrapy.selector import HtmlXPathSelectorfrom weatherhk.items import HKOCurrentItemimport datetime, re
  16. 16. spiders/ (2/5)class HKOCurrentSpider(BaseSpider): name = "HKOCurrentSpider" #allowed_domains = [""] start_urls = [ "" ]
  17. 17. spiders/ (3/5)def parse(self, response): hxs = HtmlXPathSelector(response) stations = [] # Getting weather data from each stations. tx ="//pre[1]/text()").re([^n]*n)
  18. 18. spiders/ (4/5) for i in tx: if 度,i): data = HKOCurrentItem() data[time] = int(dt) data[station] = self.station.code(i) data[temperature] = int(re.findall(ud+,i)[0]) stations.append(data)
  19. 19. spiders/ (5/5) return stations
  20. 20. (1/2)class HKOCurrentPipeline(object): def process_item(self, item, spider): station = self.db[item[station]] storeditem = dict(item.__dict__)[_values]
  21. 21. (2/2) try: if temperature in storeditem: lasttime = station.find({temperature: {$gt:0}}).sort(time, -1).limit(1) if lasttime[0][time] != storeditem[time]: id = self.insert(storeditem) return item