python: least-squares estimation?
Have a look at SciPy.  It's got matrix operations.
I know how to implement least-squares with elementary matrix decomposition and other operations, but how can I do it in Python? (I've never tried to use matrices in Python)

(clarification edit to satisfy the shoot-first-and-ask-questions-later -1'er)
I was looking for help to find out how to use numerical programming in Python. Looks like numpy and scipy are the way to go. I was looking for how to use them, but I found a tutorial.