Confused, are languages like python, ruby single threaded? unlike say java? (for web apps)
Yes Ruby and Python can handle multi-threading, but for many cases (web) is better to rely on the threads generated by the http requests from the client to the server. Even if you generate many threads on a same application to low the runtime cost or to handle many task at time, in a web application case that's usually too much time, no one will wait happily more than some fractions of a second for the response of your application in a single page, it's more wise to use AJAX (Asynchronous JavaScript And XML) techniques: make sure the design of your web shows up rapidly, and make an asynchronous insertion of those hard-coding things later.
That does not mean that multi-threading is useless for web! It's highly recommended to low the charge of your server if you want to run recursive-complicated-hardcore-applications (not for a website, I mean), but what that thing return must end in files or in databases, so then could be softly served by a http response.
I was reading how Clojure is 'cool' because of its syntax + it runs on the JVM so it is multithreaded etc. etc.
Are languages like ruby and python single threaded in nature then? (when running as a web app).
What are the underlying differences between python/ruby and say java running on tomcat?
Doesn't the web server have a pool of threads to work with in all cases?