A class with a method that can only be assigned a specific number of times

statelatch.py

class StateLatch(object):
    def __init__(self, changes_until_latched=2):
        self._state = None
        self.latch_count = changes_until_latched

    @property
    def state(self):
        return self._state

    @state.setter
    def state(self, value):
        if self.latch_count > 0 and self._state != value:
            self._state = value
            self.latch_count -= 1

if __name__ == '__main__':
    # Here is how to use a StateLatch:
    # Instantiate the class:
    x = StateLatch()
    # Show the state
    print(x.state)
    # Assign the state property three times
    # By default, the StateLatch will freeze ("latch") after 2 assignments
    x.state = 'One'
    x.state = 'Two'
    x.state = 'Three'
    # This will print "Two"
    print(x.state)