类型错误：sqlalchemy properties>class'sqlalchemy.orm.attributes.InstrumentedAttribute'

Question

我有以下sqlalchemy类（简化）：

class Persons(Base):
    __tablename__ = 'm_persons'
    birthDate = db.Column(db.Date, nullable=True)
    @hybrid_property
    def age(self):
        bd = self.birthDate
        return relativedelta(date.today(), bd).years
    @age.expression
    def age(cls):
        bd = cls.birthDate
        return relativedelta(date.today(), bd).years

当我使用属性将值打印为

^{pr2}$

它能正确地打印出人的年龄。现在，当我尝试在查询中使用该属性时，例如：

Persons.query.filter(Persons.age >= min_age).all()

然后我得到了以下错误：

TypeError: relativedelta only diffs datetime/date

我理解为cls.birthDate是类型

class 'sqlalchemy.orm.attributes.InstrumentedAttribute'

所以问题是我缺少什么来获得属性birthDate的值？在

当然，我一直在“google”搜索并阅读了doc，但找不到它不起作用的原因或解决方案。在

任何帮助都将不胜感激。在

***编辑**** 错误的痕迹：

File "/Users/ext334/Dev/python/asocio/app/members/forms.py", line 174, in __init__
    self.person.choices = listPersons(gender=subscription.gender, min_age=subscription.min_age, max_age=subscription.max_age)
  File "/Users/ext334/Dev/python/asocio/app/members/forms.py", line 31, in listPersons
    print(Persons.query.join(Members).filter(Persons.age >= min_age, Persons.age <= max_age, extract('year',Persons.birthDate) >= minBirthYear, extract('year',Persons.birthDate) <= maxBirthYear, Persons.sex == gender).order_by(Members.lastname, Members.firstname))
  File "/Users/ext334/Dev/python/venv36/lib/python3.6/site-packages/sqlalchemy/ext/hybrid.py", line 867, in __get__
    return self._expr_comparator(owner)
  File "/Users/ext334/Dev/python/venv36/lib/python3.6/site-packages/sqlalchemy/ext/hybrid.py", line 1066, in expr_comparator
    owner, self.__name__, self, comparator(owner),
  File "/Users/ext334/Dev/python/venv36/lib/python3.6/site-packages/sqlalchemy/ext/hybrid.py", line 1055, in _expr
    return ExprComparator(cls, expr(cls), self)
  File "/Users/ext334/Dev/python/asocio/app/members/models.py", line 235, in age
    return relativedelta(date.today(), cls.birthDate).years
  File "/Users/ext334/Dev/python/venv36/lib/python3.6/site-packages/dateutil/relativedelta.py", line 102, in __init__
    raise TypeError("relativedelta only diffs datetime/date")
TypeError: relativedelta only diffs datetime/date

完整查询：

Persons.query.join(Members).filter(Persons.age >= min_age, Persons.age <= max_age, extract('year',Persons.birthDate) >= minBirthYear, extract('year',Persons.birthDate) <= maxBirthYear, Persons.sex == gender).order_by(Members.lastname, Members.firstname)

全班同学：

class Persons(Base):
    """
    Description of a person
    """
    __tablename__ = 'm_persons'
    user_id = db.Column(db.Integer, db.ForeignKey('users.id', ondelete='CASCADE', onupdate='CASCADE'))
    family_id = db.Column(db.Integer, db.ForeignKey('m_families.id', ondelete='CASCADE', onupdate='CASCADE'))

    birthDate = db.Column(db.Date, nullable=True)
    sex = db.Column(db.String(1), nullable=False, default='U') # U = unknown, F = Female, M = Male


    # return the age in years, not rounded

    @hybrid_property
    def age(self):
        return relativedelta(date.today(), self.birthDate).years

    @age.expression
    def age(cls):
        return relativedelta(date.today(), cls.birthDate).years

Answer 1

好吧，我找到了一个解决办法，或者也许我更了解它是如何工作的。 在@年龄.表情您可以执行数据库的功能。所以我决定计算这里面的年龄@年龄.表情基于MySQL

代码如下：

@age.expression
def age(cls):
    return func.year(func.from_days(func.to_days(date.today()) - func.to_days(cls.birthDate)))

基本上，这是计算从出生日期到现在之间的年数。所以flask sqlalchemy查询是

^{pr2}$

生成的sql语句是：

SELECT m_persons.id AS m_persons_id, m_persons.date_created AS m_persons_date_created, m_persons.date_modified AS m_persons_date_modified, m_persons.user_id AS m_persons_user_id, m_persons.family_id AS m_persons_family_id, m_persons.`birthDate` AS `m_persons_birthDate`, m_persons.sex AS m_persons_sex FROM m_persons INNER JOIN users ON users.id = m_persons.user_id WHERE year(from_days(to_days(%s) - to_days(m_persons.`birthDate`))) >= %s AND year(from_days(to_days(%s) - to_days(m_persons.`birthDate`))) <= %s AND EXTRACT(year FROM m_persons.`birthDate`) >= %s AND EXTRACT(year FROM m_persons.`birthDate`) <= %s AND m_persons.sex = %s ORDER BY users.lastname, users.firstname

因此@年龄.表情返回year(from_days(to_days(%s) - to_days(m_persons.birthDate)))，这在查询中得到了很好的理解

作为总结，我想说的是@年龄.表情只能应用数据库函数，不能真正对列本身进行操作。在