import bpy, bmesh

ob = bpy.context.active_object        
vertex_name = 'Group'                   
find = ob.vertex_groups.get(vertex_name)
me = ob.data   
if find:        
    bpy.ops.object.mode_set(mode='EDIT') 
    bpy.ops.object.vertex_group_set_active(group=vertex_name)
    bpy.ops.object.vertex_group_select()            
        
    bm = bmesh.from_edit_mesh(me)            
    bordi = [ e for e in bm.edges if e.select ]            
    bmesh.ops.subdivide_edges(bm,edges=bordi,use_grid_fill=True,cuts=1)
me.update()   ##################################################Blender Crash! i think only when vertex group are present