`final` keyword equivalent for variables in Python?

Question

I couldn\'t find documentation on an equivalent of Java\'s final in Python, is there such a thing?

I\'m creating a snapshot of an object (used for restorati

Answer 1

An assign-once variable is a design issue. You design your application in a way that the variable is set once and once only.

However, if you want run-time checking of your design, you can do it with a wrapper around the object.

class OnePingOnlyPleaseVassily(object):
    def __init__(self):
        self.value = None
    def set(self, value):
        if self.value is not None:
            raise Exception("Already set.")
        self.value = value

someStateMemo = OnePingOnlyPleaseVassily()
someStateMemo.set(aValue) # works
someStateMemo.set(aValue) # fails

That's clunky, but it will detect design problems at run time.