copy_vertex_groups.py

import bpy

active = bpy.context.active_object

for ob in bpy.context.selected_objects:
    me_source = active.data
    me_target = ob.data

    # sanity check: do source and target have the same amount of verts?
    if len(me_source.vertices) != len(me_target.vertices):
        print('ERROR: objects {} and {} have different vertex counts.'.format(active.name,ob.name))
        continue

    vgroups_IndexName = {}
    for i in range(0, len(active.vertex_groups)):
        groups = active.vertex_groups[i]
        vgroups_IndexName[groups.index] = groups.name
    data = {}  # vert_indices, [(vgroup_index, weights)]
    for v in me_source.vertices:
        vg = v.groups
        vi = v.index
        if len(vg) > 0:
            vgroup_collect = []
            for i in range(0, len(vg)):
                vgroup_collect.append((vg[i].group, vg[i].weight))
            data[vi] = vgroup_collect
    # write data to target
    if ob != active:
        # add missing vertex groups
        for vgroup_idx, vgroup_name in vgroups_IndexName.items():
            #check if group already exists...
            already_present = 0
            for i in range(0, len(ob.vertex_groups)):
                if ob.vertex_groups[i].name == vgroup_name:
                    vgroup_name = vgroup_name+'_from_'+active.name
                    vgroups_IndexName[vgroup_idx] = vgroup_name
            # ... if not, then add
            if already_present == 0:
                ob.vertex_groups.new(name=vgroup_name)
        # write weights
        for v in me_target.vertices:
            for vi_source, vgroupIndex_weight in data.items():
                if v.index == vi_source:

                    for i in range(0, len(vgroupIndex_weight)):
                        groupName = vgroups_IndexName[vgroupIndex_weight[i][0]]
                        groups = ob.vertex_groups
                        for vgs in range(0, len(groups)):
                            if groups[vgs].name == groupName:
                                groups[vgs].add((v.index,),
                                   vgroupIndex_weight[i][1], "REPLACE")