binds = {}
finance_engine = create_engine(url1)
binds.update(dict.fromkeys(finance_metadata.sorted_tables, finance_engine))
binds.update(dict.fromkeys([Employee, Customer, Invoice], finance_engine))
staff_engine = create_engine(url2)
binds.update(dict.fromkeys(staff_metadata.sorted_tables, staff_engine))
binds.update(dict.fromkeys([Project, Hour], staff_engine))
session = sessionmaker(binds=binds)()
With sqlalchemy how to dynamically bind to database engine on a per-request basis