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comp.lang.ruby

How to use ReXML "in the wild"?

Kenneth McDonald

12/16/2008 1:23:00 AM

I'd very much like to use ReXML's XPATH features to extract info from
Google's financial info pages, but find that Rexml chokes on the
Javascript, here's the result of trying to read in a page with this
bit of code:

require "rexml/document"
require 'net/http'
Net::HTTP.start('finance.google.com') do |http|
response = http.get('/finance?fstype=ii&q=NYSE:WAT')
rdoc = REXML::Document.new(response.body)
end

==========
Output:

/usr/local/lib/ruby/1.8/rexml/parsers/treeparser.rb:92:in `parse':
#<RuntimeError: Illegal character '&' in raw string
" (REXML::ParseException)
(function(){
var d=navigator.userAgent.toLowerCase().indexOf("msie")!=-1;function
e(){var b=document.styleSheets;for(var a=b.length-1;a>=0;--a){var
c=b[a].href;if(c)if(c.indexOf("styles/finance_")!=-1||
c.indexOf("styles_")!=-1)return b[a]}return null}function f(){var
b=e();if(b){var a=b.rules;return
a.length>0&&a[a.length-1].selectorText==".lastFinanceRule"}return false}
function g(){if(document.scripts)for(var b=0;b">
/usr/local/lib/ruby/1.8/rexml/text.rb:91:in `initialize'
2 Answers

Peter Szinek

12/16/2008 1:41:00 AM

0

Hi Kenneth,
> I'd very much like to use ReXML's XPATH features to extract info from
> Google's financial info pages, but find that Rexml chokes on the
> Javascript, here's the result of trying to read in a page with this
> bit of code:

Don't try that ;) REXML in the wild == epic FAIL. At this level, you might
want to try Hpricot or Nokogiri. At a bit higher level, scRUBYt!
You can read about web scraping in Ruby here (my most succesfull article
ever, was even mentioned in Learning Ruby from O'Reilly):

http://www.rubyra.../data-extraction-for-web-20-screen-scraping-in-...

> Is there a good way to get around this problem? If, not, I guess it's
> back to regular expressions...

Web scraping with regular expressions is almost never a good idea.

Try scRUBYt!:

require 'rubygems'
require 'scrubyt'

data = Scrubyt::Extractor.define do
fetch 'http://finance.google.com/finance?fstype=ii&q=NYS...

body '/html/body' do
revenue '/div[4]/div[2]/table/tr[2]' do
ending_9_27 '/td[2]'
ending_6_28 '/td[3]'
end

gross_profit '/div[4]/div[2]/table/tr[2]' do
ending_9_27 '/td[2]'
end
end
end

puts data.to_xml

output:

<root>
<body>
<revenue>
<ending_9_27>386.31</ending_9_27>
<ending_6_28>398.77</ending_6_28>
</revenue>
<gross_profit>
<ending_9_27>386.31</ending_9_27>
</gross_profit>
</body>
</root>


HTH,
Peter
___
http://s...
http://www.rubyra...

Phlip

12/16/2008 3:48:00 AM

0

Kenneth McDonald wrote:

> I'd very much like to use ReXML's XPATH features to extract info from
> Google's financial info pages, but find that Rexml chokes on the
> Javascript, here's the result of trying to read in a page with this
> bit of code:

I have studied REXML for many years, and I still can't figure out how to get it
to recognize an &mdash; or similar advanced entity.

Like the other responder said, give up while you still can. libxml-ruby is also
stable enough to give a shot - oh yeah, except it crashes on non-tiny inputs.

Aaaand...

> /usr/local/lib/ruby/1.8/rexml/parsers/treeparser.rb:92:in `parse':
> #<RuntimeError: Illegal character '&' in raw string

That's because REXML and your web browser disagree on the definition of
well-formed. Your browser accepts a naked & inside a JavaScript tag, but REXML
does not. REXML is technically correct, and your browser would have accepted
&amp;&amp; here, but...

> a.length>0&&a[a.length-1].selectorText==".lastFinanceRule"}return false}

....browsers cannot correctly interpolate & appearing inside JavaScript literal
strings, because some lowlife coder using Notepad might have actually wanted
"&amp;" when they wrote "&amp;" - such as with document.write().

So, because REXML cannot accept normal HTML, due to hits and misses of standards
compliance on all sides - you are better off with a dedicated parser!

--
Phlip