Set up an infinite Blender background (beveled plane), with Camera, Focus-empty, and DOF

Set-Up-Blender-Infinite-Background.py

import math
import bpy

def add_infinite_background(coll_name = None):
    mesh = bpy.data.meshes.new("InfiniteBackground")
    obj = bpy.data.objects.new(mesh.name, mesh)
    col = bpy.data.collections.get("Collection")
    col.objects.link(obj)
    bpy.context.view_layer.objects.active = obj

    verts = [
        ( 1.0,  1.0,  0.0), 
        ( 1.0, -1.0,  0.0),
        (-1.0, -1.0,  0.0),
        (-1.0,  1.0,  0.0),
        (-1.0, -1.0,  2.0),
        (-1.0,  1.0,  2.0),
    ]
    edges = []
    faces = [[0, 1, 2, 3,], [3, 2, 4, 5]]

    mesh.from_pydata(verts, edges, faces)
    return obj.name

def bevel_mesh(obj_name):
    bpy.data.objects[objname].select_set(True)

    bpy.ops.object.modifier_add(type='BEVEL')
    bpy.context.object.modifiers["Bevel"].width = 0.3
    bpy.context.object.modifiers["Bevel"].segments = 8
    bpy.ops.object.shade_smooth()
    
    
objname = add_infinite_background()
bevel_mesh(objname)
bpy.ops.transform.resize(value=(10, 10, 10))





# Create Focus:
empty = bpy.ops.object.empty_add(type='PLAIN_AXES', location=(0, 0, 1))

# Create camera:
bpy.ops.object.camera_add(
    enter_editmode=False, 
    location=(8, 0, 1.5), 
    rotation=(math.pi/2, 0, math.pi/2)
)
# Add constraint for look-at:
bpy.ops.object.constraint_add(type='TRACK_TO')
bpy.context.object.constraints["Track To"].track_axis = 'TRACK_NEGATIVE_Z'
bpy.context.object.constraints["Track To"].target = bpy.data.objects["Empty"]
bpy.context.object.constraints["Track To"].up_axis = 'UP_Y'

# Set DOF:
bpy.context.object.data.dof.use_dof = True
bpy.context.object.data.dof.focus_object = bpy.data.objects["Empty"]