Is there any way to convert Wikitext to Markdown in python?

You can use pandoc for this. Try online converter.

Since is something that I need, I packaged both together:

http://bitbucket.org/wikier/mw2md

So now it's easier to perform both tasks.

Not sure it does what you want, but you might want to check out Pyandoc: a Python wrapper for Pandoc.

You can go from wikitext to html and then go from html to markdown. Not exactly straight forward, but i know no alternatives.