How to get any random list value in an n-dimensional matrix/array in python?

Suppose we have some predefined positions statements in a 2d or 3d space (e.g. generated by a robot arm with the axis/joints x, y, z, a, b). How do we get any position statement (same format x, y, z, a, b) in between these points in Python (SciPy, NumPy, MatPlotLab, etc...)?

E.g. "What is the position statement for x = -2.5 and y = 152.8"

For better understanding, I have attached a small illustration of my problem.