Run only last python function call within some timeframe?

Question

Let's say I have a function that updates some internal states of the application:

def on_change(*args, **kwargs):
    pass  # some compute intensive state change

This function can run up to hundred times a second (due to many mousewheel events triggering the update) - I would only like to execute the above function once and only the last call should be executed.

What is the best design pattern for managing such a situation? The only way I can think of is spawning a separate thread for each on_change call and share a variable between them, but this sounds overly messy...

Thanks!

Read up on class threading.Timer and cancel()

stovfl
– stovfl

2020-05-01 17:03:41 +00:00
Commented May 1, 2020 at 17:03 — stovfl
– stovfl, Commented May 1, 2020 at 17:03

Paul Cornelius · Accepted Answer · 2020-05-03 08:07:32Z

1

class Waiter:
    def __init__(self):
        self.args = ()
        self.kwargs = {}
        self.changed = False

    def on_change(self, *args, **kwargs):
        # This is the event handler
        # It does nothing but save the latest arguments
        self.args = args
        self.kwargs = kwargs
        self.changed = True

    def tick(self):
        # Call this function once per second, or whatever
        if self.changed:
            # Do your updates, using self.args and self.kwargs
            self.changed = False

Since you mentioned mouse events you are evidently writing a GUI application. All GUI engines, in my experience, have timers and the ability to call functions on a periodic basis. Use that capability to call tick periodically.

answered May 3, 2020 at 8:07

Paul Cornelius

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