#SWITCH_use_target
#SWITCH_use_group

import bpy

# find VertexGroup index

vertex_index = -1
for i in bpy.data.objects[objname].vertex_groups:
    if (i.name == vertex_grp):
        vertex_index = i.index

if (vertex_index >= 0):
    srcmesh = bpy.data.objects[objname].data
    dstmesh = bpy.data.objects[target_obj].data
    dstindex = 0
    for srcv in srcmesh.vertices:
        for grp in srcv.groups:
            if ( grp.group == vertex_index ):
                srcv.co = dstmesh.vertices[dstindex].co
                break
        dstindex += 1