Knot-style Parametric Function Script ( Python )

In my ongoing quest to eliminate or supersede all things Matlab, I present a functional solution to the problem of extruding along arbitrary contours, written in python.
This is a reaction to http://www.thingiverse.com/thing:7080, itself a derivative of http://www.thingiverse.com/thing:6923. Credit to both these authors for the concept and motivation.
Parameters are specified at the top of the script. A closed curve in 3D is specified as f:t→(x,y,z) a parametric function of t. A closed curve in 2D is specified as f:s→(x,y) and is used as the cross-section to extrude along the 3D curve.
Bonus : If you manually specify the "crosssection" matrix, which is a lost of [x,y] points around the perimeter, you can extrude arbitrary cross-sections.
download, cut, edit, steal, modify, repost, use, go.
update : I added knot.py, which simply explicitly defines the knot equations at the top and adds a couple integer parameters, similar too http://www.thingiverse.com/thing:6923.



Instructions
requires python, numpy
edit the functions and s,t ranges in the script
for knot.py, just play around with the integers at the top of the file
python stextrude.py myoutput.stl
might want to adjust resolution if the script takes too long