Set all shader attributes to a new prefixed and indexed string

set_shader_attribute.py

import pymel.core as pm

# This will replace the values in all selected objects (based on order of selection) to "<new_name>_<index in selection>"
# Feel free to replace all these variables to whatever specifics you need.
shader_type = 'aiSurface'
use_selection = True
attribute = 'aovid'
new_name = 'assetID'
padding = 2

for index, shader in enumerate(pm.ls(type=shader_type, sl=use_selection)):
    shader.attr(attribute).set('%s_%{PAD}d'.format(PAD='0' + padding) % (prefix, index)