In 2.79 there is dupli_list_create
and bunch of attributes to get from it:
https://docs.blender.org/api/2.79/bpy.types.DupliObject.html#bpy.types.DupliObject
According to the change log it was removed in recent version:
https://docs.blender.org/api/current/change_log.html?highlight=dupli_list
What is analog for 2.8?