使用sqlalchemy从壁板关联表中删除元组

Question

我想从关联表中删除行，这是对组表的辅助表。

class Groups(db.Model):
    __tablename__ = 'groups'
    group_id = db.Column(db.Integer(), Sequence('groups_id_seq') , primary_key=True)
    group_name = db.Column(db.String())
    group_desc = db.Column(db.String())
    ngo_id = db.Column(db.String(), db.ForeignKey('ngo.ngo_id'))
    delete = db.Column(db.Boolean())
    group_donors = db.relationship('Donor', secondary=groups_donor_table, backref='groups')
    def __init__(self, group_name=None, group_desc=None, ngo_id=None, delete=True):
        self.group_name = group_name
        self.group_desc = group_desc
        self.ngo_id = ngo_id
        self.delete=delete

---

关联表

groups_donor_table=db.Table('groups_donor_table',
                    db.Column('group_id', db.Integer, db.ForeignKey('groups.group_id'), nullable=False),
                    db.Column('donor_id', db.Integer, db.ForeignKey('donor.id'), nullable=False),
                    db.PrimaryKeyConstraint('group_id', 'donor_id')
                )

---

和删除行的代码

def delete_group_donors(group_id, json):
    donor_ids = json['delete_donors']
    group = db.session.query(Groups).filter_by(group_id=group_id).first()
    for donor_id in donor_ids:
     group_donor=db.session.query(groups_donor_table).filter_by(group_id=group_id, donor_id=donor_id).first()
        print group_donor
        group.group_donors.remove(group_donor)
        db.session.commit()

我能够检索数据并在表中添加，但无法删除行。

错误----

File "/home/mayur/Desktop/sahaj-backend/app.py", line 393, in update_group delete=delete_group_donors(group_id, details) File "/home/mayur/Desktop/sahaj-backend/app.py", line 432, in delete_group_donors group.group_donors.remove(group_donor) File "/home/mayur/.local/lib/python2.7/site-packages/sqlalchemy/o‌​rm/collections.py", line 1054, in remove fn(self, value) ValueError: list.remove(x): x not in list

Answer 1

您要删除的是(group_id, donor_id)元组。您根本没有理由需要在groups_donor_table上手动操作，因为关系group_donors已经为您处理。您需要从group_donors中删除的不是(group_id, donor_id)元组，而是具有id等于donor_id的Donor实例。

做到这一点的一种更直接的方法是简单地构建应保留的新捐赠者列表：

donor_ids_set = set(donor_ids)
group.group_donors = [donor for donor in group.group_donors if donor.id not in donor_ids_set]