Q: Do we have anything functionally equivalent in Python to the Ruby version manager 'rvm'?
(RVM lets you easily switch completely between different versions of the ruby interpreter and different sets of gems (modules). Everything concerning download-build-install-switch of interpreter(-s) and gems gets taken care of by invoking rvm. It is all run under your regular user account.)
Yes, it is virtualenv along with virtualenvwrapper.
update: you may install both at once with virtualenv burrito.
Update: the correct answer is now probably pyenv.
For scientific computing, the corresponding tool is anaconda.