Method if_exists

cassandra/cqlengine/query.py:1191–1201

Check the existence of an object before an update or delete. If the update or delete isn't applied, a LWTException is raised.

(self)

        return clone

    def if_exists(self):
        """
        Check the existence of an object before an update or delete.

        If the update or delete isn't applied, a LWTException is raised.
        """
        if self.model._has_counter:
            raise IfExistsWithCounterColumn('if_exists cannot be used with tables containing counter columns')
        clone = copy.deepcopy(self)
        clone._if_exists = True
        return clone

    def update(self, **values):
        """