Python 终端未构建数据库

Question

我正在用 Python 构建一个聊天工具。

当我通过

db.create_all()

自动创建数据库时，出现以下错误：

>>> db.create_all()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\Praktikant2\AppData\Local\Programs\Python\Python311\Lib\site-packages\flask_sqlalchemy\extension.py", line 887, in create_all
    self._call_for_binds(bind_key, "create_all")
  File "C:\Users\Praktikant2\AppData\Local\Programs\Python\Python311\Lib\site-packages\flask_sqlalchemy\extension.py", line 858, in _call_for_binds
    engine = self.engines[key]
             ^^^^^^^^^^^^
  File "C:\Users\Praktikant2\AppData\Local\Programs\Python\Python311\Lib\site-packages\flask_sqlalchemy\extension.py", line 639, in engines
    app = current_app._get_current_object()  # type: ignore[attr-defined]
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Praktikant2\AppData\Local\Programs\Python\Python311\Lib\site-packages\werkzeug\local.py", line 508, in _get_current_object
    raise RuntimeError(unbound_message) from None
RuntimeError: Working outside of application context.

This typically means that you attempted to use functionality that needed
the current application. To solve this, set up an application context
with app.app_context(). See the documentation for more information.
>>>

我有以下代码：

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from datetime import datetime

app = Flask(__name__)

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///db.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)

class Message(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    user = db.Column(db.String(200), nullable=True)
    content = db.Column(db.String(500), nullable=True)
    created_at = db.Column(db.DateTime(), default=datetime.utcnow)

with app.app_context():
    db.create_all()

@app.route("/")
def start_page():
    return "<h1>Hello World!</h1>"

if __name__ == "__main__":
    app.run(debug=True)

我做错了什么以及如何解决它？

Answer 1

您所要做的就是强制应用程序的上下文。连接并实例化后，添加以下行：

app.app_context().push()

您的代码将是：

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///db.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)
app.app_context().push()

然后，在终端上：

1。 Python（或 Python3） 2.从应用程序导入应用程序 3.从应用程序导入数据库 4. db.create_all()