未映射Flasksqlalchemy insert

1 from app import app, db 2 3 product_tags = db.Table('association', 4 db.Column('product_id', db.Integer, db.ForeignKey('product.id')), 5 db.Column('tag_name', db.Integer, db.ForeignKey('tag.name')) 6 ) 7 8 class Product(db.Model): 9 id = db.Column(db.Integer, primary_key=True) 10 title = db.Column(db.String(128)) 11 description = db.Column(db.Text) 12 image = db.Column(db.String(64)) 13 link = db.Column(db.String(256)) 14 price = db.Column(db.Float()) 15 timestamp = db.Column(db.DateTime) 16 expiration = db.Column(db.String(6)) 17 tags = db.relationship('Tag', secondary=product_tags, 18 backref=db.backref('product', lazy='dynamic')) 19 20 def __init__(self, title, description, image, link, price, timestamp, expiration, tags): 21 self.title = title 22 self.description = description 23 self.image = image 24 self.link = link 25 self.price = price 26 self.timestamp = timestamp 27 self.expiration = expiration 28 self.tags = tags 29 print self.title 30 31 def __repr__(self): 32 return '<Title %r, Description %r, Image %r, Link %r, Price %r, Timestamp %r, Expires %r, Tags %r>' % (self.title, self.description, self.image, sel 33 34 class Tag(db.Model): 35 name = db.Column(db.String(32), primary_key=True) 36 37 def __init__(self, name): 38 self.name = name 39 40 def __repr__(self): 41 return '<Tag %r>' % self.name

1 from app import db 2 from app.models import Product, Tag, product_tags 3 from datetime import datetime 4 5 imagefolder = 'static/img/' 6 7 title = 'product' 8 description = 'description' 9 image = 'image.jpg' 10 link = 'http://link.com' 11 price = 2000.00 12 expiration = '' 13 tags = ['tag1','tag2'] 14 15 newtags = [] 16 17 def create_product(title, description, image, link, price, expiration, tags): 18 image = imagefolder + image 19 tag_assoc = [] 20 for tag in tags: 21 tagcheck = Tag.query.filter_by(name=tag).first() 22 if tagcheck == None: 23 tag_assoc.append(Tag(tag)) 24 else: 25 newtags.append(tag) 26 27 product = Product(title, description, image, link, price, datetime.utcnow(), expiration, tag_assoc) 28 create_assoc(newtags) 29 return product 30 31 def create_assoc(newtags): 32 title_search = Product.query.filter_by(title=title).first() 33 for tag in newtags: 34 assoc = product_tags.insert().values(product_id=title_search.id, tag_name=tag) 35 db.session.add(assoc) 36 db.session.commit() 37 38 if __name__ == '__main__': 39 product = create_product(title, description, image, link, price, expiration, tags) 40 db.session.add(product) 41 db.session.commit() 42 create_assoc(newtags)

11:11 ~/shop $ python addproduct.py product Traceback (most recent call last): File "addproduct.py", line 39, in <module> product = create_product(title, description, image, link, price, expiration, tags) File "addproduct.py", line 28, in create_product create_assoc(newtags) File "addproduct.py", line 35, in create_assoc db.session.add(assoc) File "/home/username/.local/lib/python2.7/site-packages/sqlalchemy/orm/scoping.py", line 114, in do return getattr(self.registry(), name)(*args, **kwargs) File "/home/username/.local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 1358, in add raise exc.UnmappedInstanceError(instance) sqlalchemy.orm.exc.UnmappedInstanceError: Class 'sqlalchemy.sql.expression.Insert' is not mapped

1条回答

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1楼 · 发布于 2024-05-13 19:39:19

我可以看到的第一个错误是，在您的模型中——您的关联正确地有两个外键，但是标记的外键是一个Integer，但是Tag类中的主键是一个String——它们应该匹配。除此之外，这些模型看起来还不错。

你还应该能够简化你的create_product功能：

def create_product(title, description, image, link, price, expiration, tags):
    image = imagefolder + image
    tag_list = []
    for tag in tags:
        tagcheck = Tag.query.filter_by(name=tag).first()
        if tagcheck is None:
            tag_list.append(Tag(tag))
        else:
            tag_list.append(tagcheck)
    product = Product(title, description, image, link, price, datetime.utcnow(), expiration, tag_list)
    return product

这可以很容易地移动到您的__init___构造函数中。在您的示例中，您直接处理关联表，但根本不必——只要相信ORM做正确的事情，这就是SQLAlchemy的优点。

下面是一个产品模型的示例：

class Product(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(128))
    description = db.Column(db.Text)
    image = db.Column(db.String(64))
    link = db.Column(db.String(256))
    price = db.Column(db.Float())
    timestamp = db.Column(db.DateTime)
    expiration = db.Column(db.String(6))
    tags = db.relationship('Tag', secondary=product_tags,
            backref=db.backref('products', lazy='dynamic'))

    def __init__(self, title, description, image, link, price, timestamp, expiration, tags):
        self.title = title
        self.description = description
        self.image = image
        self.link = link
        self.price = price
        self.timestamp = timestamp
        self.expiration = expiration

        for tag in tags:
            tagcheck = Tag.query.filter_by(name=tag).first()
            if tagcheck is None:
                self.tags.append(Tag(tag))
            else:
                self.tags.append(tagcheck)

    def __repr__(self):
        return '<{}, {}>'.format(self.title, ":".join([x.name for x in self.tags]))

为了测试它，首先让我们向系统添加几个标记：

ta = Tag('cat')
tb = Tag('dog')
db.session.add_all([ta, tb])
db.session.commit()

>>> Tag.query.all()
[<Tag u'cat'>, <Tag u'dog'>]

现在让我们添加一个使用这些标签的产品，外加一个新标签。

p = Product(
    'title',
    'description',
    'image',
    'link',
    0.0,
    datetime.now(),
    'expiry',
    ['dog','cat','horse']
)
db.session.add(p)
db.session.commit()

当我们创建这个产品时，构造器接受这三个字符串标记中的每一个，并说“嘿，这个名称的标记已经存在了吗？”如果是，则使用它，如果不是，则使用该名称创建新标记。SQLAlchemy足够聪明，能够将新标记添加到会话中，并在产品提交时提交它。

>>> Tag.query.all()
[<Tag u'cat'>, <Tag u'dog'>, <Tag u'horse'>]

现在让我们找到所有带有狗标签的产品（假设已经添加了更多的产品）。

>>> tag = Tag.query.get('dog')
>>> products = tag.products
>>> [x.title for x in products]
['title','other','examples']

再说一次，我根本就没有碰过关联表，没有必要。SQLAlchemy节省了我们的精力。

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