def apply(self):
        'play the journal back onto the base dictionary.'
        for change in self.changes:
            if change.action == '+':
                self.base[change.key] = change.value
            elif change.action == '-':
                del self.base[change.key]
        self.wipe()
play the journal back onto the base dictionary.
recipes/Python/521882_Journal_Dictionary/recipe-521882.py