Distance between point and a line (from two points)
np.cross returns the z-coordinate of the cross product only for 2D vectors. So the first norm in the accepted answer is not needed, and is actually dangerous if p3 is an array of vectors rather than a single vector. Best just to use
d=np.cross(p2-p1,p3-p1)/norm(p2-p1)which for an array of points p3 will give you an array of distances from the line.