Problema:
from sqlalchemy.sql import func
suma = db.session.query(func.sum(Ventas.importe)).all()
> [(Decimal(24.01),)]
SoluciĆ³n:
from sqlalchemy.sql import func
suma = db.session.query(func.sum(Ventas.importe)).scalar()
> 24.01
date_start = date(2019, 6,16)
date_end = date(2019, 6,16)
variable = Tabla.query.filter(Tabla.campo_fecha.between(date_start, date_end)).all()