The easiest way for 3D visualization in Python is VPython.
For example, to draw a curve in the shape of a square, it's just:
square = curve(pos=[(0,0),(0,1),(1,1),(1,0),(0,0)])
This is vastly easier than MayaVI, VTK, OpenGL, etc.
Another easy option is matplotlib's 3D graphics. It's better on the quantitative details, but not as simple, fast, and interactive for the 3D part.
