Use trackball as scroll wheel

trackball.py

#!/usr/bin/env python3
# This script opens the given device and maps its
# axis movements to scroll wheel events,
# so you can use a trackball to scroll any window.
# You will need to run `xinput disable $DEVICE` to
# prevent it from also moving the cursor.
DEVICE = "Primax Kensington Eagle Trackball"

import evdev
import pynput
from pynput.mouse import Button, Controller

def main():
    global DEVICE
    inputDevice = None

    # find the device
    devices = [evdev.InputDevice(fn) for fn in evdev.list_devices()]
    for device in devices:
        if device.name == DEVICE:
            inputDevice = evdev.InputDevice(device.path)
            break

    if inputDevice is None:
        raise "Device not found"

    # get a mouse controller
    mouse = Controller()

    for event in inputDevice.read_loop():
        if event.code == 0: mouse.scroll(event.value / 10, 0)
        elif event.code == 1: mouse.scroll(0, event.value / -10)
        # 11: wheel
        # 272: left click
        # 273: right click
        #else: print(event.code, event.type, event.value)

if __name__ == '__main__':
    main()