addAttributeCallback(attribute, function, addon)

# ../<MOD>/addons/eventscripts/gungame/scripts/custom/gg_sample/gg_sample.py
 
from gungame.core.players.shortcuts import setAttribute
from gungame.core.players.shortcuts import addAttributeCallBack
from gungame.core.players.shortcuts import removeAttributeCallBack
from gungame.core.players.shortcuts import removeCallBacksForAddon
 
def load():
    # Set the custom attribute "myattribute" on all connected players
    setAttribute('#all', 'myattribute', 0)
 
    # Add the attribute callback
    # (this will call on "callbackFunction" any time "myattribute" is set
    #  via the __setitem__ or __setattr__ method)
    addAttributeCallBack('myattribute', callbackFunction, 'gg_sample')
 
def unload():
    '''
    When you unload the custom addon, so long as the correct "addon" argument
    was provided, "removeCallBackForAddons('addon_name_being_unloaded')" will be called,
    which in this case will be "removeCallBackForAddon('gg_sample')". Therefore, the
    following "removeAttributeCallBack('myattribute')" and "removeCallBacksForAddon('gg_sample')" is not necessary, but moreso exists for the sake of showing how to use
    the function.
    '''
    # Remove the custom attribute "myattribute" from all players
    removeAttributeCallBack('myattribute')
 
    # Remove all custom attribute callbacks for this addon
    removeCallBacksForAddon('gg_sample')
 
def callbackFunction(name_of_the_attribute, value_to_be_checked):
    '''
    This callback function can be used for more than 1 attribute, so that you can
    register multiple attribute callbacks. All that you have to do is check the
    name of the attribute (the first argument). The second argument is the value
    of the attribute. If you raise an error during your callback, the attribute
    will not be set to the attempted value.
    '''
    if name_of_the_attribute == 'myattribute':
        # Make sure the value is from 0-10
        if value_to_be_checked in range(0, 11):
            pass
        else:
            raise ValueError('Value must be between 0 and 10!')