python sqlalchemy AttributeError: 'BaseQuery' object 没有属性 'id'

Question

我正在尝试使用来自另一个表“营养值”的数据来设置表的 foreign_key 列

class NutritionalValues(db.Model):
    __tablename__ = 'nutritionalvalues'
    id = db.Column(db.Integer, primary_key=True)
    item = db.Column(db.String(200), nullable=False)
    calories = db.Column(db.Float, nullable=False)
    totalfat = db.Column(db.Float, nullable=False)

通过使用

consumed_nutrionalvalue_id = NutritionalValues.query.filter_by(item=consumed_item).id

其中“consumed_item”是与 NutritionalValues 表的一行的“item”值的字符串完全匹配的字符串

但我得到了错误

AttributeError: 'BaseQuery' object has no attribute 'id'

Traceback (most recent call last)
File "/Users/benjamattesjaroen/helloPython/env/lib/python3.7/site-packages/flask/app.py", line 2463, in __call__
return self.wsgi_app(environ, start_response)
File "/Users/benjamattesjaroen/helloPython/env/lib/python3.7/site-packages/flask/app.py", line 2449, in wsgi_app
response = self.handle_exception(e)
File "/Users/benjamattesjaroen/helloPython/env/lib/python3.7/site-packages/flask/app.py", line 1866, in handle_exception
reraise(exc_type, exc_value, tb)
File "/Users/benjamattesjaroen/helloPython/env/lib/python3.7/site-packages/flask/_compat.py", line 39, in reraise
raise value
File "/Users/benjamattesjaroen/helloPython/env/lib/python3.7/site-packages/flask/app.py", line 2446, in wsgi_app
response = self.full_dispatch_request()
File "/Users/benjamattesjaroen/helloPython/env/lib/python3.7/site-packages/flask/app.py", line 1951, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Users/benjamattesjaroen/helloPython/env/lib/python3.7/site-packages/flask/app.py", line 1820, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/Users/benjamattesjaroen/helloPython/env/lib/python3.7/site-packages/flask/_compat.py", line 39, in reraise
raise value
File "/Users/benjamattesjaroen/helloPython/env/lib/python3.7/site-packages/flask/app.py", line 1949, in full_dispatch_request
rv = self.dispatch_request()
File "/Users/benjamattesjaroen/helloPython/env/lib/python3.7/site-packages/flask/app.py", line 1935, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/Users/benjamattesjaroen/helloPython/app.py", line 65, in index
consumed_nutrionalvalue_id = NutritionalValues.query.filter_by(item=consumed_item).id
AttributeError: 'BaseQuery' object has no attribute 'id'

但是明确的“营养价值”确实有一个名为“id”的列？ 如何访问存储在表的该列中的 integer 以进行查询？

Answer 1

以下是查询

NutritionalValues.query.filter_by(item=consumed_item)

要获得 object（orm 中的这个 o），您可以使用.first()或许多结果.all()

NutritionalValues.query.filter_by(item=consumed_item).first()

你现在有一个正常的 object 你可以做 pythonic 的方法来比如成员访问。

这很有趣，因为您可以在获得结果的执行之前构建动态查询。