#import blender stuff
import bpy

#loop through all objects in the scene
#bpy.context.scene.objects is a list
for obj in bpy.context.scene.objects:
    #use only real opbject, not the camera or lamp
    if obj.type == 'MESH':
        #select the current object
        obj.select = True
        #remove the current selected object (which will always be obj)
        bpy.ops.object.delete()

#create a new cube object
bpy.ops.mesh.primitive_cube_add(location=(0, 0, 0))

#define a function which will be called every frame change
def my_func(scene):
    obj = scene.objects[0]
    obj.location.x = scene.frame_current/50
    print("frame #", scene.frame_current)

#remove all handlers
for i in range( len( bpy.app.handlers.frame_change_pre ) ):
        bpy.app.handlers.frame_change_pre.pop()

#append handler
bpy.app.handlers.frame_change_pre.append(my_func)