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Web Data Crawling vs Web Data Scraping Python

May 30, 2012Category : Blog Web Scraping
Web Data Crawling vs Web Data Scraping Python

One of our favourite quotes has been, ‘If a problem changes by an order, it becomes a different problem’ and in this lies the answer to – Data Crawling vs Data Scraping.

Data Crawling means dealing with large data-sets where you develop your crawlers (or bots) which crawl to the deepest of the web pages. Data scraping, on the other hand, refers to retrieving information from any source (not necessarily the web). It’s more often the case that irrespective of the approaches involved, we refer to extracting data from the web as scraping (or harvesting) and that’s a serious misconception.

 

Data Crawling vs Data Scraping

1. Scraping data does not necessarily involve the web. Data scraping tools that help in data scraping could refer to extracting information from a local machine, a database. Even if it is from the internet, a mere “Save as” link on the page is also a subset of the data scraping universe. Data crawling, on the other hand, differs immensely in scale as well as in range. Firstly, crawling = web crawling which means on the web, we can only “crawl” data. Programs that perform this incredible job are called crawl agents or bots or spiders (please leave the other spider in spiderman’s world). Some web spiders are algorithmically designed to reach the maximum depth of a page and crawl them iteratively (did we ever say crawl?). While both seem different, web scraping vs web crawling are mostly the same.

2. The web is an open world and the quintessential practising platform of our right to freedom. Thus a lot of content gets created and then duplicated. For instance, the same blog might be posted on different pages and our spiders don’t understand that. Hence, data de-duplication (affectionately dedup) is an integral part of web data crawling service. This is done to achieve two thingskeep our clients happy by not flooding their machines with the same data more than once; and saving our servers some space. However, deduplication is not necessarily a part of web data scraping.

Web Crawling Services & Web Scraping Services

3. One of the most challenging things in the web crawling space is to deal with the coordination of successive crawls. Our spiders have to be polite with the servers, that they do not piss them off when hit.  This creates an interesting situation to handle. Over some time, our spiders have to get more intelligent (and not crazy!). They get to develop learning to know when and how much to hit a server, how to crawl data feeds on its web pages while complying with its politeness policies. While both seem different, web scraping vs web crawling are mostly the same. 

4. Finally, different crawl agents are used to crawling different websites and hence you need to ensure they don’t conflict with each other in the process. This situation never arises when you intend to just crawl data.

 

Data crawling vs data scraping

On a concluding note, when talking about web scraping vs web crawling. ‘Scraping’ represents a very superficial node of crawling which we call extraction, and that again requires few algorithms and some automation in place.

P.S. This post does not intend to offend anyone who uses the terms ‘scraping’ and ‘crawling’ interchangeably. But purely wishes to create awareness for those interested in the Big Data domain.

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13 thoughts on “Web Data Crawling vs Web Data Scraping Python
  • Amey Desai

    It would be interesting to know you’re crawling and scraping approaches also. Whether you have a distributed crawler architecture, adaptive crawlers etc. Another thing I would like to read on you’re part is how you follow robots.txt and the term ‘politeness’ associated with crawling. In a place saturated with web development, it would be really cool if folks can roll out posts on the technical aspects of web crawling.

  • Arpan

    Amey,

    Thanks for your comments. We’ll gradually get to the technical aspects of our infrastructure and technology in our future posts.

  • Anonymous

    What throughput does your platform support ? I have about 200k sites to be crawled on a daily basis. Will your system be able to support that ?

  • Hanumesh Palla

    What about “SCRAPY” … an opensource for web crawling and scraping. If there is anything regarding it

  • Anonymous

    Question I have:

    Are coding skills transferable between creating a search engine AND web scraping a website?

    By web scraping I mean softwares functions such as those provided by Outwit Hub Pro or Helium Scraper or
    NeedleBase (extinct.)

    I have been told web scraping a website requires the following coding skills:
    Python , Regular Expressions (Regex) , XPath

    In other words, are the coding skills learned in web scraping transferable to creating a private search engine to index a particular website online in whole to keep up to date with all site changes (such as new product promotions)?

    By the way, the website I am keeping tabs on has a new web page for each new product promotion.

    There is no centralized page where I can view a list of latest product promotions.

    Please enlighten.

    Thanks a million.

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  • Jayaraj Chanku

    Hi Arpan,
    Thanks for this valuable article. You made the words clear and differentiated them based on factual ideas. Thanks for sharing this post.

  • Julian

    Short and strict to the point. Great one! It is recommended that a proxy service should be used while crawling to maximize the value. Thanks!

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