def alter_column_family(self, keyspace, column_family, column_validation_classes=None, **cf_kwargs):

        self._conn.set_keyspace(keyspace)
        cfdef = self.get_keyspace_column_families(keyspace)[column_family]

        for k, v in cf_kwargs.iteritems():
            v = self._convert_class_attrs(k, v)
            setattr(cfdef, k, v)

        if column_validation_classes:
            for (colname, value_type) in column_validation_classes.items():
                cfdef = self._alter_column_cfdef(cfdef, colname, value_type)

        self._system_update_column_family(cfdef)
Alters an existing column family.
dataset/ETHPy150Open pycassa/pycassa/pycassa/system_manager.py/SystemManager.alter_column_family