"KiCAD's python" is the python 2.7 installed in the KiCAD installation directories.
The problem with installing NumPy is that I get "not supported on this platform" when I try to install it from a variety of whl files. When installing from pip directly, I get errors that look like failure to compile.
I'm creating a few functions for checking pads, silkscreen, stencils, and drill/via holes.
I'm documenting progress here on what I'm now calling KiPadCheck
I've been getting good performance on basic checks for pads. DRC for hole to track spacing takes a little longer, but still reasonable (10 seconds) on my 75mm x 75mm board. I'm now starting to code non-orthogonal rectangular checks (mask (*edit: was silk) to rotated text). There really are no algorithms for that specifically, but intersection of convex polygons is the closest step up. Since the calculations will start to take longer if larger board, and especially tracks are being used, then I thought it would be prudent to install a numerical library. Another alternative is shapely, which has whl files available as well, but it also is a binary whl, similar to NumPy.