Blender Python API example: detection of changes in mesh object (edit mode)

example_mesh_changes.py

import bpy


def cb_scene_update(context):
    """
    """
    edit_obj = bpy.context.edit_object
    if edit_obj is not None and edit_obj.is_updated_data is True:
        print(edit_obj)
    #print('>>> Update')

class StopCallback(bpy.types.Operator):
    """Tooltip"""
    bl_idname = "scene.stop_callback"
    bl_label = "Stop Callback"
    
    @classmethod
    def poll(cls, context):
        return cb_scene_update in bpy.app.handlers.scene_update_post

    def execute(self, context):
        print('Removing callback ...')
        bpy.app.handlers.scene_update_post.remove(cb_scene_update)
        print('DONE')
        return {'FINISHED'}


class StartCallback(bpy.types.Operator):
    """Tooltip"""
    bl_idname = "scene.start_callback"
    bl_label = "Start Callback"
    
    @classmethod
    def poll(cls, context):
        return cb_scene_update not in bpy.app.handlers.scene_update_post

    def execute(self, context):
        print('Adding callback ...')
        bpy.app.handlers.scene_update_post.append(cb_scene_update)
        print('DONE')
        return {'FINISHED'}


class SceneTestPanel(bpy.types.Panel):
    """
    Creates a Panel in the Scene properties window
    """
    bl_label = "Scene Test Panel"
    bl_idname = "OBJECT_PT_scene_test"
    bl_space_type = 'PROPERTIES'
    bl_region_type = 'WINDOW'
    bl_context = "scene"

    def draw(self, context):
        layout = self.layout

        scene = context.scene

        row = layout.row()

        row = layout.row()
        row.operator("scene.start_callback")

        row = layout.row()
        row.operator("scene.stop_callback")


def register():
    bpy.utils.register_class(SceneTestPanel)
    bpy.utils.register_class(StartCallback)
    bpy.utils.register_class(StopCallback)


def unregister():
    bpy.utils.unregister_class(SceneTestPanel)
    bpy.utils.unregister_class(StartCallback)
    bpy.utils.unregister_class(StopCallback)


if __name__ == '__main__':
    register()