import bpy
import math
import bmesh
import random

# This makes it easy to keep revising and running the script
bpy.ops.object.select_all(action='SELECT')
bpy.ops.object.delete(use_global=False)

# ccmp = Color Component
def random_ccmp():
	return random.randrange(0, 1000) / 1000.0

def random_color():
	return (random_ccmp(), random_ccmp(), random_ccmp(), 1.0)

mat = bpy.data.materials.new(name="VertexColorMaterial")
mat.use_nodes = True
bsdf = mat.node_tree.nodes.get("Principled BSDF")
color_node = mat.node_tree.nodes.new(type='ShaderNodeVertexColor')
color_node.layer_name = "Col"
mat.node_tree.links.new(color_node.outputs['Color'], bsdf.inputs['Base Color'])

def create_colored_cube(stair):
	center = (0, stair * 2, stair)
	bpy.ops.mesh.primitive_cube_add(location=center)
	cube = bpy.context.active_object
	cube.scale = (2, 2, 0.25)

	bpy.ops.object.mode_set(mode='EDIT')
	mesh = bmesh.from_edit_mesh(cube.data)
	color_layer = mesh.loops.layers.color.new("Col")

	for i, face in enumerate(mesh.faces):
		face_color = random_color()
		for loop in face.loops:
			loop[color_layer] = face_color

	bmesh.update_edit_mesh(cube.data)
	bpy.ops.object.mode_set(mode='OBJECT')
	cube.data.materials.append(mat)

# Globals in Python:  Create a variable outside the function, say "global" inside
stair = 0
def create_stair():
	global stair # It'll make a local variable without this
	if bpy.context.mode != "OBJECT":
		return None
	create_colored_cube(stair)
	stair += 0.5
	if stair < 30:
		return 0.2
	return None

bpy.app.timers.register(create_stair)