In some situations, you may want Maya to run a specific MEL command or script before rendering each frame, and another MEL command or script after rendering. For instance, if your scene contains a very large complex surface, which you do not want to work on, you could run a MEL command before rendering to display the surface (so it renders), and run another MEL command after rendering to hide the surface.
To run Pre Render MEL scripts or Post Render MEL scripts, see Run Pre Render MEL or Post Render MEL scripts.
print("Time to render my Maya scene, called\"bingo.mb"\");
Pre and post render layer scripts are called only during 3D rendering, and are not called during render target rendering.