Blender Python : How to get Boolean Union of two objects?

run.py

import bpy

def Union(name_a, name_b, new_one_name):
    # Create a boolean modifier named 'my_bool_mod' for the cube.
    mod_bool =  bpy.data.objects[name_a].modifiers.new('my_bool_mod', 'BOOLEAN')
    # Set the mode of the modifier to DIFFERENCE.
    mod_bool.operation = 'UNION' #'DIFFERENCE'
    # Set the object to be used by the modifier.
    mod_bool.object = bpy.data.objects[name_b]
    bpy.context.view_layer.objects.active = bpy.data.objects[name_a]
    # Apply the modifier.
    res = bpy.ops.object.modifier_apply(apply_as='DATA', modifier = 'my_bool_mod')
    
    bpy.data.objects[name_b].select_set(True) # 2.8+
    bpy.ops.object.delete()
    bpy.data.objects[name_a].name = new_one_name
    return res