python - Filter on a literal column in sqlalchemy -

With sqlalchemy, how do I filter on a literal column?

So I have a query.

  session.query (Object.att1, Object.att2, literal_column ('x'). Label ('xVar'))   
 Where now I Literally column! = X.  
 For this reason I want to do this, because I have two questions which I have found in a joint query, so every query has a literal column and the identifier who asks is. And sometimes I have to filter the union query to return one of only two questions.   
 
 
 I think the answer is:  
 let me query the query in a new subquery And then I can filter that question, as an example.  
  union = session.query (Object .att1, object.att2, literal_column ('x'). Label ('xVar')). Subquery () toFilter = session.query (unionQuery) .filter (unionQuery.c.xvar! = 'X')