Crawling a Web Page with Scrapy

Hi… all today i’m going to share how to crawl a web page with scrapy. See my previous post for installation here.

Its always best to create directory for learning any language or programming.

Open Terminal (cntrl+Alt + T)

mkdir (name of the directory)

cd /directoryname

To create a new project in scrapy

scrapy startproject sample

now change the directory to

cd sample

type the command ls

sample   scrapy.cfg

now cd sample

again  –   ls

_init__.py   items.py   pipelines.py 
  settings.py   spiders

scrapy created these files within sample(name of project) folder.

If you already know django or python means you can easily understand these . If not don’t worry i will try to explain as much as i can .

  • scrapy.cfg: the project configuration file
  • sample/: the project’s python module, you’ll later import your code from here.
  • sample/items.py: the project’s items file.
  • sample/pipelines.py: the project’s pipelines file.
  • sample/settings.py: the project’s settings file.
  • sample/spiders/: a directory where you’ll later put your spiders.
  • __init__.py –  to initialize Python Packages and also consider this directory as Python Package.

Now ,it times to get into scrapy and crawl a page

Things we have to for crawling a web page are:

  • Define items in items.py
  • Write a spider to crawl a page and extract items
  • Writing an pipelines.py  to store the extracted Items

Things to do in items.py

from scrapy.item import Item, Field
class SampleItem(Item):
    # define the fields for your item here like:
    # name = Field()
    title=Field()  // for title of a page
    link=Field() // for links of the page
    desc=Field() //for  description of a page

Things to do with  Spiders/

To create Spider Scrapy genspider (name) (domain name) or

simply create one sample.py in spiders folder.

mydomain.py (i created mydomain.py in spiders folder of the project)

from scrapy.spider import BaseSpider
from scrapy.selector import HtmlXPathSelector
from sample.items import SampleItem

class DmozSpider(BaseSpider):
    name = “dmoz”
    allowed_domains = [“dmoz.org”]
    start_urls = [
        “http://www.dmoz.org/Computers/Programming/Languages/Python/Books/”,
        “http://www.dmoz.org/Computers/Programming/Languages/Python/Resources/”
    ]
    def parse(self, response):
       sel = HtmlXPathSelector(response)
       sites = sel.select(‘//ul/li’)
       items = []
       for site in sites:
           item = SampleItem()
           item[‘title’] = site.select(‘a/text()’).extract()
           item[‘link’] = site.select(‘a/@href’).extract()
           item[‘desc’] = site.select(‘text()’).extract()
           items.append(item)
       return items

Lets explain what i did above,

For spiders three things are necessary

  • name
  • start_url
  • parse method

name must be unique for every page

start_urlslist of urls which we want to crawl

parsemethod for extracting data from webpage.

allow_domains allows pages with given domains and restricts others pages

Thats it .. now run our file and see what’s happening .

To run a  spider

scrapy crawl [name of the spider]

so in our code spider name is ‘dmoz’ . 

scrapy crawl dmoz

In terminal you can see like this

if your code is correct i mean without any errors you can see Spider opened and crawled and closed like below

2013-11-27 16:09:20+0530 [dmoz] INFO: Spider opened
2013-11-27 16:09:20+0530 [dmoz] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2013-11-27 16:09:20+0530 [scrapy] DEBUG: Telnet console listening on 0.0.0.0:6023
2013-11-27 16:09:20+0530 [scrapy] DEBUG: Web service listening on 0.0.0.0:6080
2013-11-27 16:09:21+0530 [dmoz] DEBUG: Crawled (200) <GET http://www.dmoz.org/Computers/Programming/Languages/Python/Books/&gt; (referer: None)
2013-11-27 16:09:21+0530 [dmoz] DEBUG: Scraped from <200 http://www.dmoz.org/Computers/Programming/Languages/Python/Books/&gt;
{‘desc’: [u’\r\n\r\n ‘],
‘images’: [],
‘link’: [u’/’],
‘title’: [u’Top’]}
2013-11-27 16:09:21+0530 [dmoz] DEBUG: Scraped from <200 http://www.dmoz.org/Computers/Programming/Languages/Python/Books/&gt;
{‘desc’: [], ‘images’: [], ‘link’: [u’/Computers/’], ‘title’: [u’Computers’]}
2013-11-27 16:09:21+0530 [dmoz] DEBUG: Scraped from <200 http://www.dmoz.org/Computers/Programming/Languages/Python/Books/&gt;
{‘desc’: [],
‘images’: [],
‘link’: [u’/Computers/Programming/’],
‘title’: [u’Programming’]}

Want to Store the crawled details as json or csv ?

To store the crawled details as json run this command

 scrapy crawl dmoz -o items -t json

now you can see the items.json in your project directory.

Scrapy Shell

Scrapy comes with inbuilt tool for debugging and testing our code and makes developers job easily.

Inside project directory run   this command scrapy shell

you can see like this !!

2013-11-27 16:23:04+0530 [scrapy] DEBUG: Web service listening on 0.0.0.0:6080
[s] Available Scrapy objects:
[s] item {}
[s] settings <CrawlerSettings module=<module ‘sample.settings’ from ‘/home/bala/scrapycodes/sample/sample/settings.pyc’>>
[s] Useful shortcuts:
[s] shelp() Shell help (print this help)
[s] fetch(req_or_url) Fetch request (or URL) and update local objects
[s] view(response) View response in a browser

now lets check this

fetch(“http://www.google.co.in&#8221;)

2013-11-27 16:25:23+0530 [default] INFO: Spider opened
2013-11-27 16:25:29+0530 [default] DEBUG: Crawled (200) <GET http://www.google.co.in&gt; (referer: None)
[s] Available Scrapy objects:
[s] hxs <HtmlXPathSelector xpath=None data=u'<html itemscope=”” itemtype=”http://sche’&gt;
[s] item {}
[s] request <GET http://www.google.co.in&gt;
[s] response <200 http://www.google.co.in>  # Things to note
[s] settings <CrawlerSettings module=<module ‘sample.settings’ from ‘/home/bala/scrapycodes/sample/sample/settings.pyc’>>
[s] spider <BaseSpider ‘default’ at 0x3cde3d0>
[s] Useful shortcuts:
[s] shelp() Shell help (print this help)
[s] fetch(req_or_url) Fetch request (or URL) and update local objects
[s] view(response) View response in a browser

hxs -> html xpath selector

now we have response of the requested url .

lets get the title of the page .

hxs.select(“//title”) 

<HtmlXPathSelector xpath=’//title’ data=u'<title>Google</title>’>]

it returns the selector element (with html tags)

we want text  of the tag

hxs.select(“//title”).extract()

[u'<title>Google</title>’]

extract -> used to extract element from page

Things to note:  Results are in list and u’ represents unicode.

Lets try this !!!

hxs.select(“//title/text()“).extract()[0]
 u’Google’

For xpath learning use this   Xpath.

Thats it … Happy coding ..

Scrapy Beginning Tutorial

Hi to all. Today i started learning scrapy .Here i’m going to start scrapy from the beginning ..

What is Scrapy?

Scrapy is an application framework for crawling websites and extracting  structured data which can be used for a wide range of useful applications, like data mining, information processing etc.

Take a look at the documentation of scrapy  for more information here

Scrapy was written in Python. Hence you must some knowledge in python to work in scrapy.

For those who are beginners in python i would suggest these books “A Byte of Python ”  & “Learning Python the HardWay” (or) “Dive into Python“.

For those who have already knowledge in python remember this . Scrapy supports python 2.6 and 2.7 . Scrapy doesn’t support Python3.

Lets see the installation here.

Pre requisites :

  • Python 2.7
  • lxml
  • Opensssl
  • Pip or easy_install (Python package Managers)

To install Scrapy Open Terminal and type(cntrl + Alt + T)

$ pip install Scrapy

or

$ easy_install Scrapy

After installation type  $ scrapy

Scrapy 0.18.4 – no active project

Usage:
  scrapy <command> [options] [args]

Available commands:
  bench         Run quick benchmark test
  fetch         Fetch a URL using the Scrapy downloader
  runspider     Run a self-contained spider (without creating a project)
  settings      Get settings values
  shell         Interactive scraping console
  startproject  Create new project
  version       Print Scrapy version
  view          Open URL in browser, as seen by Scrapy

  [ more ]      More commands available when run from project directory

Use “scrapy <command> -h” to see more info about a command

It shows the installed scrapy version and other details .
Thats it .. From my next post we will get started with Coding …

Happy Times !!! Thanks !!!!!!!!