Remove handler feature in Engine

I recently encountered the cases where I would like to remove a handler and optionally replace it with another one. The following code is used:

def remove_handler(engine, handler, event_name):
    assert event_name in engine._event_handlers    
    engine._event_handlers[event_name] = [(h, args, kwargs) 
                                          for h, args, kwargs in engine._event_handlers[event_name] 
                                            if h != handler]

@alykhantejani @jasonkriss what do you guys think about inserting such method into Engine ? cc @anmolsjoshi

[jasonkriss]

Got it! Thanks for the added context. Helps a lot. Let’s go ahead and add it then.

[vfdev-5]

Would it maybe more clear here to use two stats_collectors rather than having to remember to remove the handler?

@jasonkriss it means that we need to copy previous code to reinit another stats_collectors …

Is there a benefit to cleaning up after it finishes?

More on the context: I wrote a basic time profiler that collects times spent in handlers, batch preparation and process function. To do this the profiler adds manually its handlers in the special order: the first and the last handlers on the events. Profiler adds its handlers once the run is called to avoid the situation when user adds other handlers after profiler.attach(trainer) is called. So, once trainer.run(train_loader) is done, profiler computed what it needs and should remove its added handlers. Otherwise, on the second call of trainer.run(train_loader) there will be twice more attached handlers and times collection will be difficult or even faulty.

EDIT: even for symmetry with the methods we already have: add, has, event handler. Remove is missing 😃