Python 使用值初始化数据库

我有一个简单的问题。当我运行flask应用程序时，我想直接向数据库添加一个初始值，如下所示

if __name__ == '__main__':
    db.init_app(app)
    with app.app_context():
        db.create_all()

    user = UserModel.find_by_name('user')
    if not user:
        user = UserModel('name', 'password')
        user.save_to_db()
    app.run() 

这样做会导致以下错误：

Traceback (most recent call last):
  File "C:\Users\Jeffrey T\Documents\2019_2023UPenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site-packages\sqlalchemy\util\_collections.py", line 1020, in __call__
    return self.registry[key]
KeyError: 48452

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:/Users/Jeffrey T/Documents/2019_2023UPenn/PennLabs/ChallengeSpr2020/PennLabsServerChallengeSpr2020/index.py", line 18, in <module>
    jen = UserModel.find_by_name('jen')
  File "C:\Users\Jeffrey T\Documents\2019_2023UPenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\models\user.py", line 54, in find_by_name
    return cls.query.filter_by(username=username).first()
  File "C:\Users\Jeffrey T\Documents\2019_2023UPenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site-packages\flask_sqlalchemy\__init__.py", line 514, in __get__
    return type.query_class(mapper, session=self.sa.session())
  File "C:\Users\Jeffrey T\Documents\2019_2023UPenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site-packages\sqlalchemy\orm\scoping.py", line 78, in __call__
    return self.registry()
  File "C:\Users\Jeffrey T\Documents\2019_2023UPenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site-packages\sqlalchemy\util\_collections.py", line 1022, in __call__
    return self.registry.setdefault(key, self.createfunc())
  File "C:\Users\Jeffrey T\Documents\2019_2023UPenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site-packages\sqlalchemy\orm\session.py", line 3286, in __call__
    return self.class_(**local_kw)
  File "C:\Users\Jeffrey T\Documents\2019_2023UPenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site-packages\flask_sqlalchemy\__init__.py", line 136, in __init__
    self.app = app = db.get_app()
  File "C:\Users\Jeffrey T\Documents\2019_2023UPenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site-packages\flask_sqlalchemy\__init__.py", line 987, in get_app
    raise RuntimeError(
RuntimeError: No application found. Either work inside a view function or push an application context. See http://flask-sqlalchemy.pocoo.org/contexts/.

回溯（最近一次呼叫最后一次）：
文件“C:\Users\Jeffrey T\Documents\2019_2023; upenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site packages\sqlalchemy\util\\ u collections.py”，第1020行，在调用中__
返回self.registry[项]
密钥错误：48452
在处理上述异常期间，发生了另一个异常：
回溯（最近一次呼叫最后一次）：
文件“C:/Users/Jeffrey T/Documents/2019_2023; upenn/PennLabs/ChallengeSpr2020/PennLabsServerChallengeSpr2020/index.py”，第18行，在
jen=UserModel。通过名称（“jen”）查找
文件“C:\Users\Jeffrey T\Documents\2019_2023; upenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\models\user.py”，第54行，按名称查找
返回cls.query.filter_by（username=username）.first（）
文件“C:\Users\Jeffrey T\Documents\2019\U 2023UPenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site packages\flask\u sqlalchemy\\uuuuu init\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu__
返回类型.query\u类（映射器，session=self.sa.session（））
文件“C:\Users\Jeffrey T\Documents\2019_2023; upenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site packages\sqlalchemy\orm\scoping.py”，第78行，在调用中__
返回self.registry（）
文件“C:\Users\Jeffrey T\Documents\2019_2023; upenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site packages\sqlalchemy\util\\ u collections.py”，第1022行，在调用中__
返回self.registry.setdefault（项，self.createfunc（））
文件“C:\Users\Jeffrey T\Documents\2019_2023; upenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site packages\sqlalchemy\orm\session.py”，第3286行，在_u调用中__
返回自功率等级（**本地功率）
文件“C:\Users\Jeffrey T\Documents\2019_2023; upenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site packages\flask\u sqlalchemy\\ uuuuuuuuuuuuuuuuuuu init.py”，第136行，在uuuuuuuuuu init中__
self.app=app=db.get_app（）
文件“C:\Users\Jeffrey T\Documents\2019_2023; upenn\PennLabs\ChallengeSpr2020\PennLabsServerChallengeSpr2020\venv\lib\site packages\flask\u sqlalchemy\\uuuuu init\uuuuuuuuuuuuuuuu.py”，第987行，在get\u应用程序中
引发运行时错误(
RuntimeError:找不到应用程序。请在视图函数内工作或推送应用程序上下文。请参阅http://flask-sqlalchemy.pocoo.org/contexts/.

---

有没有办法解决这个问题？

第一次创建表时，向表中添加数据的正确方法如下

from sqlalchemy import event
# import your initialized db
from app import db

class Department(db.Model):
    __tablename__ = 'department'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(64), index=True, unique=True)
    email = db.Column(db.String(64), index=True)

@event.listens_for(Department.__table__, 'after_create')
def create_departments(*args, **kwargs):
    db.session.add(Department(name='Customer Service', email='abc@domain.com'))
    db.session.add(Department(name='IT', email='def@domain.com'))
    db.session.commit()

---

第一次在您的配置设置序列中运行

db.create_all（）

时，它将创建您的数据库架构，并触发

create_departments

函数，用您想要的数据填充表格。

您的应用程序是什么？请给我们更多解释