I'm trying to get started with unit testing in Python and I was wondering if someone could explain the advantages and disadvantages of doctest and unittest.  
What conditions would you use each for?
If you're just getting started with the idea of unit testing, I would start with doctest because it is so simple to use. It also naturally provides some level of documentation. And for more comprehensive testing with doctest, you can place tests in an external file so it doesn't clutter up your documentation.
I would suggest unittest if you're coming from a background of having used JUnit or something similar, where you want to be able to write unit tests in generally the same way as you have been elsewhere.
Python - doctest vs. unittest