Flask 使用值初始化数据库答案

【问题标题】：Flask initialize database with valuesFlask 使用值初始化数据库
【发布时间】：2020-09-25 07:26:33
【问题描述】：

我有一个简单的问题。当我运行我的烧瓶应用程序时，我想直接向数据库添加一个初始值，就像这样

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()

这样做会给我以下错误：

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/.

有什么办法解决这个问题吗？

【问题讨论】：

你的应用是什么？给我们更多的解释

标签： python api web flask sqlalchemy

【解决方案1】：

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()

db.create_all() 第一次在您的配置设置序列中运行时，它将创建您的数据库架构并触发create_departments 函数以使用您想要的数据填充表。

【讨论】：