Edge length equalize for Blender

import bpy
from mathutils import Vector

bl_info = {
    "name": "Edge length equalize.",
    "author": "Michal Krupa",
    "version": (0, 1, 0),
    "blender": (2, 70, 0),
    "location": "Editmode > W",
    "warning": "",
    "description": "",
    "wiki_url": "",
    "category": "Mesh",
}


class EdgeEqualizeOperator(bpy.types.Operator):
    bl_idname = "mo.edge_equalize"
    bl_label = "Equalize edge length."

    def execute(self, context):
        ob = bpy.context.object

        if ob.type != 'MESH':
            raise TypeError("Active object is not a Mesh")

        if ob:
            self.do_equalize(ob)

        return {'FINISHED'}

    def do_equalize(self, ob):
        ob.update_from_editmode()

        me = ob.data

        if len(me.edges) < 1:
            raise ValueError("Mesh has no edges")

        edges = me.edges

        selected_edges = [i.index for i in bpy.context.active_object.data.edges if i.select == True]

        if not selected_edges:
            self.report({'ERROR'}, "You have to select some edges!")
            return

        current_mode = ob.mode

        bpy.ops.object.mode_set(mode='OBJECT', toggle=False)

        total_length = 0

        for edge in selected_edges:
            vt1 = me.edges[edge].vertices[0]
            vt2 = me.edges[edge].vertices[1]
            a_to_b_vec = me.vertices[vt1].co - me.vertices[vt2].co
            total_length += a_to_b_vec.length
            print(a_to_b_vec.length)
        median_length = total_length / len(selected_edges)

        for edge in selected_edges:
            vt1 = me.edges[edge].vertices[0]
            vt2 = me.edges[edge].vertices[1]
            center = (me.vertices[vt1].co + me.vertices[vt2].co) * .5

            for v in (me.vertices[vt1], me.vertices[vt2]):
                new_co = (v.co - center).normalized() * (median_length / 2.0)
                v.co = new_co + center

        bpy.ops.object.mode_set(mode=current_mode, toggle=False)


def register():
    bpy.utils.register_class(EdgeEqualizeOperator)


def unregister():
    bpy.utils.unregister_class(EdgeEqualizeOperator)


if __name__ == "__main__":
    register()