Question

I have the following two classes :

class DbQuery:
    def __init__(self,query):
        self.query = query

class DbResultSet:
    def __init__(self,query):
        self.result = []

And these classes are used for SQL queries and results, attributes are used to simulate enum-like functionality. A query looks as follows :

q_forum_heirarchy =\
    type(   "RtDbQuery",
            DbQuery( """SELECT level, id, parent_id, name 
                        FROM forum_heirarchy_node
                        WHERE forum_id = :f_id 
                        AND level != 0
                        ORDER BY level ASC;"""), 
            LEVEL=0, ID=1, PARENT_ID=2, NAME=3 )

Is there some way for me to copy the attributes from DbQuery into DbResultset ? I don’t want to have to embed the query in the resultset because then I would have to write db_resultset.query.LEVEL instead of db_resultset.LEVEL to get to the enum ordinals.

I see a __get_attribute__ method but I suppose this is indexed by attribute_name.

edit:

The code is invalid python, it doesn’t change the gist of what I was asking. I discovered psycopg2(database library) can do namedtuples() (python objects with the performance characters of enums), so I can’t be bothered to update it 😀

Answer 1

I think that you should use __getattr__ method. This method is used by lookup mechanism when no class attributes are found.

class DbQuery(object):
  def __init__(self,query):
        self.query = query

class DbResultSet(object):
  def __init__(self, dbquery):
        self.result = []
        self.dbquery = dbquery
  def __getattr__(self, name):
        return getattr(self.dbquery,name)