import add_arnold_attrs
reload(add_arnold_attrs)
  
import maya.cmds as cmds
import os.path
import glob
  
  
projpath = cmds.workspace(q=True, rootDirectory=True)
sourceimages_path = os.path.join(projpath, 'sourceimages')
  
# Get a list of all the .tx files
glob_pattern = os.path.join(sourceimages_path, '*.tx')
paths = glob.glob(glob_pattern)
for path in paths:
    path = path.replace('\\', '/')
  
add_arnold_attrs.add_string('mappath', paths)