If it turns out that creating tuples in the main loop ends up leading to excessive GC action, it may be worth considering changing update() to return an int with bits that correspond to the buttons that are pressed instead of a list. It would make the API a little less "pythonic" but would mean that there is no tuple or list getting created by it in the main loop.

My (potentially incorrect) understanding was that tuples were more performant and used less memory than lists, but yes, using an integer would be even better.

How I managed this in my recent relic_usb_host_gamepad library was to keep a private integer within the object which is updated during update. Then, I added boolean properties which test the integer with a bitmask to determine if the button was pressed when the mouse was last updated. Since gamepads have a whole lot of buttons, I got a little more fancy using descriptors and changed states, but that might not be necessary here.

This would look something along the lines of:

while True:
    if mouse.update():  # True if successfully read from mouse
        if mouse.left_button:  # tests against internal integer
            print("left button pressed")
        if mouse.right_button:
            print("right button pressed")

If this is how you'd like to see this working, I could draft up something along these lines.