MBE-subobject assigner [BMESH Api]

import bpy
import bmesh
import random

# getting current mode
curr_mode = bpy.context.active_object.mode
bpy.ops.object.mode_set(mode='EDIT')

bpy.context.scene.tool_settings.mesh_select_mode = (False, False, True)
mesh = bpy.context.object.data

bm = bmesh.from_edit_mesh(mesh)
assigned=[] #to trace assigned face

for f in bm.faces:
    if f in assigned:   #if already assigned
        pass            #do nothing
    else :
        f.select_set(1)                 #select
        bpy.ops.mesh.select_linked()    #select linked
        matindex=random.randint(0,4)    #generate ID
        for s in bm.faces:              #for s in faces
            if s.select:                #if selected
                s.material_index = matindex #assign m ID
                assigned.append(s)          #mark as assigned
        bpy.ops.mesh.select_all(action='TOGGLE')    #unselect

bm.select_flush(True)
#mesh.update()
bpy.ops.object.mode_set(mode=curr_mode)