Change the color in bpy

Question

I want to give the color to the human body mesh that was loaded from the .obj file as v,vn, vt,f I want to give the color with a specific formula as color=(n*e+1)/2)*225 where n is vn, normal vector, and e is sun position can be from above as (0,0,1) and the color should fill the triangle of the given normal vector.

Here is my sample code but it is not working

import bpy
import math
# Set up the scene
scene = bpy.context.scene
scene.render.engine = 'CYCLES'
# Import the human body model
bpy.ops.import_scene.obj(filepath="C:\\Users\\Desktop\\body_script\\body_triangular.obj")
# Rename the imported object
human_obj = bpy.context.selected_objects[0]
human_obj.name = "Human"
# Add a Sun lamp to the scene
bpy.ops.object.light_add(type='SUN', location=(0,0,0))
sun = bpy.data.objects['Sun']
sun.name = "Sun"
sun.data.direction = (0, 0, 1)
# Get the sun position
e = math.cos(sun.rotation_euler[0])
# Define the color function
def get_color(n, e):
    r = (n[0]*e+1)/2 * 255
    g = (n[1]*e+1)/2 * 255
    b = (n[2]*e+1)/2 * 255
    return (r, g, b)
# Loop through the vertices and set their colors
human_mesh = human_obj.data
for poly in human_mesh.polygons:
    for loop_index in range(poly.loop_start, poly.loop_start + poly.loop_total):
        n = human_mesh.loops[loop_index].normal
        color = get_color(n, e)
        if len(human_mesh.vertex_colors) == 0:
            human_mesh.vertex_colors.new()
        human_mesh.vertex_colors.active.data[loop_index].color = color

Answer 1

ok, all is not clear about what is the goal here (in my opinion).

But here are some modifications for the end of your script (with needed comments added).

Also you'll need to remove

sun.data.direction = (0, 0, 1)

because sun has no directionin its data.

def get_color(n, e):
    # blender's colors are from 0 to 1
    # so I removed "* 255"
    r = (n[0]*e+1)/2
    g = (n[1]*e+1)/2
    b = (n[2]*e+1)/2
    return (r, g, b, 1) # added "1", because vcol are rgba

# Loop through the vertices and set their colors
human_mesh = human_obj.data

# This can be done once (so outside of the loop)
if len(human_mesh.vertex_colors) == 0:
    human_mesh.vertex_colors.new()
for poly in human_mesh.polygons:
    n = poly.normal
    # as you need to use the face normal, the calculation below
    # can be done once per face
    color = get_color(n, e)
    for loop_index in range(poly.loop_start, poly.loop_start + poly.loop_total):
        #n = human_mesh.loops[loop_index].normal << this is not the face normal
        human_mesh.vertex_colors.active.data[loop_index].color = color

Using Suzanne, that gives the following result: