I am trying to use Rails to extract data from Wikipedia, based on a search term.
For example,
1) if I have the String "American Idol", I want to pass that to Wikipedia and get a list of the articles that relate to that. My goal will be to take the first 3 hyperlinks and display them on the website.
2) one step further would involve me extracting small pieces of data from Wikipedia - say the infobox, or the first few words of the wikipedia article.
Any tips?
Thanks!
You don't need to resort to screen-scraping, MediaWiki has a very comprehensive API for precisely this kind of thing. See https://github.com/jpatokal/mediawiki-gateway for a handy Ruby wrapper around it.
Alternatively, if you're only interested in data like infoboxes, see DBpedia for the database version of Wikipedia.
There is another gem that you can use: https://github.com/kenpratt/wikipedia-client
This gem seems to get just the first result of your search, but you can consult the documentation to be sure.
Regarding the content, once you get the page, the gem allows you to access the different content of the article, links, images and so on.
Use mechanize and nokogiri to do that. This is a great cheat sheet for that:
http://www.e-tobi.net/blog/files/ruby-mechanize-cheat-sheet.pdf
Mechanize is a toolbox to simulate website calls and nokogiri is an html/xml parser. It should be simple to realize that.
Related
I tried using Feedjira to assist with content analysis from newsfeeds, but it appears that RSS feeds now only link to content rather than including them with RSS as I found out in "Feedjira not adding content and author". I plan to use Feedjira to get the URL for the article, but then use Nokogiri to scrape the article and pick out the relevant parts.
The problem is that each media outlet will have a different format for their pages and I need to know the best way for Nokogiri to take the URL from the database (supplied by Feedjira) and depending on the associated feed title (also the database from Feedjira sync) scrape the page in a specific way and save it to a separate table in the database. Anyone got any suggestions?
I don't know your special use case but I'm also doing content analysis using news feeds.
Maybe you'll have a look on Readability which provides you a generic content scraper.
The problem you've encountered is that every feed generator does it a bit differently, just as with HTML generators. You can assume certain fields are going to be in place in an RDF, RSS or ATOM feed, however the author of the feed could use optional tags that you could find very useful, so you have to write code to look for them.
I wrote several feed aggregators in the past, including one that was handling well over 1000 feeds daily. By sniffing out the feed type, ATOM vs. RSS vs RDF, then I could make sensible checks for fields that were interesting given that format, and extract the data if it was available.
Pre-canned parsers get it wrong too often, either grabbing data you don't want and making a mess of the output, or skipping data you do want leaving gaps in the output, so be prepared to write code if you want it done correctly.
You'll probably want to take advantage of a backing database too, to keep track of what you looked at last and when you're supposed to look at it again; That's part of being a good network citizen. You'll also want to keep track whether a feed was down the last n times you looked so you can trim out dead sites.
When using FB or Google + I can paste a link of any website into the status update box and it will instant load information about that website with the option of flicking through thumbnail images.
How can I go about achieving this in ruby on rails? All my searches seem to bring up php methods on how to do this.
For grabbing video data info I use the Ruby Open Graph Protocol gem. Is there any thing for grabbing data the way FB and G+ do? If not is there a standard way this is done in rails/ruby, if so.. how is this done?
Kind regards
I think you're looking for something like oembed. I've found a gems for that, so I propose you to take look at it: https://github.com/judofyr/ruby-oembed or https://github.com/embedly/embedly-ruby
You should likely use a gem like http://nokogiri.org/
It allows you to work with a html page just as you would do with jQuery. Very handy.
I want to know if there is a better way of extracting info from a web page than parsing the HTML for what i'm searching. ie: Extracting movie rating from 'imdb.com'
I'm currently using the IndyHttp components to get the page and i'm using strUtils to parse the text but the content is limited.
I found plain simple regex-es to be highly intuitive and simple when dealing with good web-sites, and IMDB is a good web site.
For example the movie rating on the IMDB's movie HTML page is in a <DIV> with class="star-box-giga-star". That's VERY easy to extract using a regular expression. The following regular expression will extract the movie rating from the raw HTML into capture group 1:
star-box-giga-star[^>]*>([^<]*)<
It's not pretty, but it does the job. The regex looks for the "star-box-giga-star" class id, then it looks for the > that terminates the DIV, and then captures everything until the following <. To create a new regex like this you should use a web browser that allows inspecting elements (for example Crome or Opera). With Chrome you can simply look at the web-page, right-click on the element you want to capture and do Inspect element, then look around for easily identifiable elements that can be used to create a good regex. In this case the "star-box-giga-star" class is obviously easily identifiable! You'll usually have no problem finding such identifiable elements on good web sites because good web sites use CSS and CSS requires ID's or class'es to be able to style the elements properly.
Processing RSS feed is more comfortable.
As of the time of posting, the only RSS feeds available on the site are:
Born on this Date
Died on this Date
Daily Poll
Yet, you may make a call for adding a new one by getting in touch with the help desk.
Resources on RSS feed processing:
Relevant post here on SO.
Super Object
Wikipedia.
When scraping websites, you cannot rely on the availability of the information. IMDB may detect your scraping and attempt to block you, or they may frequently change the format to make it more difficult.
Therefore, you should always try to use a supported API Or RSS feed, or at least get permission from the web site to aggregate their data, and ensure that you're abiding by their terms. Often, you will have to pay for this type of access. Scraping a website without permission may open you up to liability on a couple legal fronts (Denial of Service and Intellectual Property).
Here's IMDB's statement:
You may not use data mining, robots, screen scraping, or similar
online data gathering and extraction tools on our website.
To answer your question, the better way is to use the method provided by the website. For non-commercial use, and if you abide by their terms, you can download the IMDB database directly and use the data from there instead of scraping their site. Simply update your database frequently, and it's a better solution than scraping the site. You could even wrap your own web API around it. Ratings are available as a standalone table.
Use HTML Tidy to convert any HTML to valid XML and then use an XML parser, maybe using XPATH or developing your own code (which is what I do).
All the answers posted cover well your generic question. I usually follow an strategy similar to the one detailed by Cosmin. I use wininet and regex for most of my web extraction needs.
But let me add my two cents at the specific subquestion on extracting imdb qualification. IMDBAPI.COM provides a query interface returning json code, which is very handy for this type of searches.
So a very simple command line program for getting a imdb rating would be...
program imdbrating;
{$apptype console}
uses htmlutils;
function ExtractJsonParm(parm,h:string):string;
var r:integer;
begin
r:=pos('"'+Parm+'":',h);
if r<>0 then
result:=copy(h,r+length(Parm)+4,pos(',',copy(h,r+length(Parm)+4,length(h)))-2)
else
result:='N/A';
end;
var h:string;
begin
h:=HttpGet('http://www.imdbapi.com/?t=' + UrlEncode(ParamStr(1)));
writeln(ExtractJsonParm('Rating',h));
end.
If the page you are crawling is valid XML, i use SimpleXML to extract infos. Works pretty well.
Resource:
Download link.
I need to generate seo meta keyword tags based upon user generated wiki content.
Say I have an article and a predefined list of keywords/phrases, is there some good method to grab matched article keywords? Keywords may not be of one word length and will be given a predefined weight as to which keywords are used first. Some implementation of Nokogiri seems the obvious choice but I wondered if there were something more complete for this exact scenario.
You could process your text thanks to a semantic API, it will give you a list of potential keywords + the score associated.
I've begun to develop this gem: https://github.com/apneadiving/SemExtractor
It still needs some improvements for error handling but it's fully operational to query the following engines:
Zemanta
Semantic Hacker from Textwise
Yahoo Boss
OpenCalais
If you're only wanting to grab keywords for the meta keyword tag, that's not really worth your time. Google doesn't pay attention to those anymore.
Here's a good post about it, with a video of Matt Cutts from Google explaining that the meta keyword tag doesn't play a part in search engine rankings.
http://www.stepforth.com/blog/2010/meta-keyword-tag-dead-seo/
What is worth your time? Good title tags.
I just have a link to a product page, at amazon. How do I get all the information (photo, price etc), in my ruby program, just using this link?
Here's the list of supported urls as disclosed by amazon for their oembed, product advertising API would come to picture only after parsing through these URLs and getting the ASINs
http://*amazon.*/gp/product/*
http://*amazon.*/*/dp/*
http://*amazon.*/dp/*
http://*amazon.*/o/ASIN/*
http://*amazon.*/gp/offer-listing/*
http://*amazon.*/*/ASIN/*
http://*amazon.*/gp/product/images/*
http://*amazon.*/gp/aw/d/*
http://www.amzn.com/*
http://amzn.com/*
I found this library (I'm using Rails)
amazon-ecs
I'm experimenting with it. Still, I'd require some kind of ID (product id?) to get details of a particular product. For example, consider this link to kindle
http://www.amazon.com/Kindle-Amazons-Wireless-Reading-Generation/dp/B00154JDAI/ref=amb_link_84372271_1?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-1&pf_rd_r=06JJGQP9J3BHKPE38SXP&pf_rd_t=101&pf_rd_p=478184871&pf_rd_i=507846
In that link, I noticed ASIN, which is B00154JDAI.
Looks like I can use this ID, to get product information (using amazon-ecs). I just need to parse the URL, to get ASIN.
Is there any other way to do it?
No, I am not going to do screen scraping, that is not a good idea anytime.
If you want to do this, the Nokogiri or hpricot libraries both allow HTML parsing and searching. However, this kind of screen-scraping is notoriously unreliable (as it may break any time Amazon decides to reorganize their HTML), so if you're planning to do this sort of thing for any length of time I'd recommend leveraging the Amazon Product Advertising API instead.
In your program: fetch the page and parse HTML. Filter out the required information. There may be some libraries in Ruby (that I am unaware of), which parse HTML.
hpricot seems to do what you want.
You should use the library Ruby/AWS (google for it, my karma is not high enough to allow external links...). It has been written exactly for that.
You might need to use the built-in Search to find the item you're looking for. After that, the API gives access to pictures, links and all usable information.