Can we parse "string" as Driver Variable?

Question

I am using scripted driver to changes image texture.

import bpy

def change_image_baby( val,min,max):
    if (min <= val <= max):
        filePath = "//baby_eyes\\eye_0%d.png" % val
        bpy.data.images["Minu Child eyes.001"].filepath = filePath
    return val

bpy.app.driver_namespace['change_image_baby'] = change_image_baby

On bone Movement by using above function as driver I am able to change the images.

Now i want to use same driver function on many other characters.

So I defined "filePath" and "image" name as object property of each character

New driver function

import bpy

def change_image(n,min,max,img,file):
    val = int(n*10)
    # img is image to be replaced and "file" is the file path
    return val
    if (min <= val <= max):
        filePath = file % val # as all my images are in sequence i replacing numbers see above code
        bpy.data.images[img].filepath = filePath

bpy.app.driver_namespace['change_image'] = change_image

and use in driver UI to parse it to custom driver

I am not able to parse string it has to be either int or float. What is the workaround to parse string as Driver Variable?

Answer 1

in this method we try to identify the object that is running the driver then we access its properties ( image and file ):

1. we add a new property to all scene objects this property is their index in the scene objects list ( we need to run this every time we add/delete an object to the scene ) :

   import bpy
   for obj in bpy.context.scene.objects :
       obj["index"] = bpy.context.scene.objects.find(obj.name)
   

2. we pass only the object index to the driver to identify it and access its properties.

   import bpy
   
   def change_image(n,min,max,index):
       obj = bpy.context.scene.objects[index]
       val = int(n*10)
       if (min <= val <= max):
           filePath = obj["file"] % val 
           bpy.data.images[obj["img"]].filepath = filePath
   
   bpy.app.driver_namespace['change_image'] = change_image
   

Answer 2

You could choose the image by number from a preset list -

import bpy

img_list = [
    ('Eyes.001','//eyes/image%d.png'),
    ('Mouth.001','//mouth/image%d.png'),
    ]

def change_image(n,min,max,img,file):
    val = int(n*10)
    # img is type of image and "file" is the file path
    if (min <= val <= max):
        filePath = img_list[file][1] % val # as all my images are in sequence i replacing numbers see above code
        bpy.data.images[img_list[file][0]].filepath = filePath

bpy.app.driver_namespace['change_image'] = change_image