exploratorty.py

import bpy
import bmesh
from mathutils import Matrix, Vector


def getDupliEdges(edges):
    dupEdges = []
    for e in edges:
        retOneEdge = bmesh.ops.duplicate(bm, geom=[e])

        dupGeom = retOneEdge["geom"]
        dupEdge = [j for j in dupGeom if isinstance(j, bmesh.types.BMEdge)]
        dupEdges.append(dupEdge[0])

    # now we're done with the original edges, we can deselect
    for edge in edges:
        edge.select = False

    # select the new ones.
    for edge in dupEdges:
        edge.select = True
    
    return dupEdges

def scaleEdges(dupEdges,factor):
    for e in dupEdges:
        mid_invert = (e.verts[0].co + e.verts[1].co) * -0.5
        edge_matrix = Matrix()
        edge_matrix[0][3] = mid_invert[0]
        edge_matrix[1][3] = mid_invert[1]
        edge_matrix[2][3] = mid_invert[2]
        bmesh.ops.scale(bm, vec=factor, space=edge_matrix, verts=e.verts)

obj = bpy.context.edit_object
mesh = obj.data
bm = bmesh.from_edit_mesh(mesh)
bm.faces.active = None

edges = [e for e in bm.edges if e.select]
dupEdges = getDupliEdges(edges)
scaleEdges(dupEdges, factor=[2.0, 2.0, 2.0])

bmesh.update_edit_mesh(mesh, True)