Coordination problem with bilinear interpolation

The problem is that there is a text file with three columns, each column is the coordinates of the point in the plan (X, Y, Z), respectively. The coordinates given with a certain step (D) in latitude (X) and longitude (Y), that is, form a regular grid. At each point (node of the grid) defined by these coordinates is the height, that is, the third coordinate (Z).
You need to search for the height of the point (Z′), which I enter from the keyboard behind my coordinates (X′,Y′). If my point does not fall into the node of the regular grid, then it is necessary to perform bilinear interpolation between the nodes of the cell into which my point falls, that is, in the square with vertices (X1,Y1; X2,Y1; X2;Y2; X1;Y2).
Please order in Delphi or Python.
And give access to the code itself.