two dimentional interpolation in matrix values

matrix_interp.py

from scipy.interpolate import interp2d
        
  def matrix_interp():
    
        mat = numpy.array([[70.45, 0, 21.78, 0],
                           [0, 0,      0,   0],
                           [105.12, 0, 1000.45, 0],
                           [0, 0, 0, 0]])
                           
        ix = numpy.where(mat != 0)
        f = interp2d(ix[0], ix[1], mat[ix].flatten(), kind='linear')
        mat2 = mat.copy()
        mat2[mat == 0] = f(range(4), range(4)).T[mat == 0]