Plane-plane intersection in python
This is solved by elementary vector computation and is not substantial/useful enough to deserve a library implementation. Work out the math with Numpy.
The line direction is given by the cross product of the two normal vectors (A, B, C), and it suffices to find a single point, say the intersection of the two given planes and the plane orthogonal to the line direction and through the origin (by solving a 3x3 system).

Computation will of course fail for parallel planes, and be numerically unstable for nearly parallel ones, but I don't think there's anything you can do.
I need to calculate intersection of two planes in form of AX+BY+CZ+D=0 and get a line in form of two (x,y,z) points. I know how to do the math, but I want to avoid inventing a bicycle and use something effective and tested. Is there any library which already implements this? Tried to search opencv and google, but with no success.