答案 0 :(得分:3)
下面的例子应该给你一个线索(假设我正确猜到Demande是声明性模型):
joined = stmt.outerjoin(Demande.__table__, Demande.grouped==stmt.c.timestep)
q = session.query(stmt.c.timestep, func.count(Demande.id)).\
select_from(joined).\
group_by(stmt.c.timestep)