How to modify mesh after import in Blender using Python? I am using Python to import a specific mesh in Blender, mesh that I want to modify after import using some sliders I have defined. So I have the defined the following function for the import:

import bpy, math, bmesh

def addGlasses(context, r):
    # import glasses object
    bpy.ops.import_scene.obj(filepath="myMesh.obj", axis_forward='-Z', axis_up='Y', filter_glob="*.obj;*.mtl")

    # select the imported object so it has a location
    ob = bpy.context.selected_objects[0]

    return ob


and then I have defined the user interface for the imported object:

#
#    User interface
#

from bpy.props import *

class MESH_OT_glasses_add(bpy.types.Operator):
   bl_idname = "mesh.glasses_add"
   bl_label = "Add glasses"
   bl_options = {'REGISTER', 'UNDO'}

   radius = FloatProperty(name="First parameter", default=1.0, min=0.01, max=100.0)

   location = FloatVectorProperty(name="Location")
   rotation = FloatVectorProperty(name="Rotation")
   # Note: rotation in radians!

   def execute(self, context):
      ob = addGlasses(context, self.radius)
      ob.location = self.location
      ob.rotation_euler = self.rotation

    return {'FINISHED'}


So I can move and rotate the object as I wish with the sliders "Location" and "Rotation" but I want also to modify some specific parts of my mesh. Practically, radius is a slider for my mesh that appears when the mesh is imported and I would like to use it's value to stretch some specific vertices for the mesh (I know which ones they are).
Is there a way to do that? Because I can't even select a single vertex after import.
Set imported object active:

ob = bpy.context.selected_objects[0]
bpy.context.scene.objects.active = ob