Beginner Blender Python tutorial code for beveling a single edge

beveling_a_single_edge.py

import bpy
import bmesh

bpy.ops.mesh.primitive_cube_add()
cube_obj = bpy.context.active_object

bpy.ops.object.editmode_toggle()

bpy.ops.mesh.select_all(action="DESELECT")
bm = bmesh.from_edit_mesh(cube_obj.data)

# make sure we can use the [] square brackets to retrieve edges
bm.edges.ensure_lookup_table()

# get reference to an edge and select it
edge = bm.edges[0]
edge.select = True

bpy.ops.mesh.bevel(offset=0.5, segments=8, affect="EDGES")

bpy.ops.object.editmode_toggle()