Python Flask 上下文 - 无法创建数据库

Question

我对 Python-Flask 很陌生。我正在开发一个应用程序，我在其中创建了以下“Main.py”脚本。 还有另一个脚本“run.py”来调用“create_app”函数并创建应用程序的实例。

但它抛出“RuntimeError: No application found.要么在视图函数内工作，要么推送应用程序上下文。”错误。

我曾在“create_app()”函数中尝试过here 中提到的选项。

在创建应用程序后，我已尝试将应用程序推送到我的“run.py”文件中的上下文。

在使用“create_app()”函数创建应用程序后，我尝试在“run.py”脚本中创建数据库，但出现如下错误部分所述的错误。

# Main.py Script Inside my application package:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

def create_app():
    app = Flask(__name__)
    app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///database.db'
    db.init_app(app)
    db.create_all()
    return app

我有另一个脚本 "run.py" ，它创建一个应用程序并运行它。

# run.py to create an instance of app and run it

from flaskblog import create_app

app = create_app()
# app.app_context().push()  # Tried this

# db.init_app(app)    # Tried this as well, after commenting the same line in "create_app()" function
# db.create_all()

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

错误 1

PS Python_Flask> & "C:/Program Files/Python38/python.exe" c:/Document/Codes/Python_Flask/run.py
C:\Program Files\Python38\lib\site-packages\flask_sqlalchemy\__init__.py:833: FSADeprecationWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future.  Set it to True or False to suppress this warning.
  warnings.warn(FSADeprecationWarning(
Traceback (most recent call last):
  File "c:/Document/Codes/Python_Flask/run.py", line 3, in <module>
    app = create_app()
  File "c:\Document\Codes\Python_Flask\flaskblog\__init__.py", line 52, in create_app
    db.create_all()
  File "C:\Program Files\Python38\lib\site-packages\flask_sqlalchemy\__init__.py", line 1039, in create_all
    self._execute_for_all_tables(app, bind, 'create_all')
  File "C:\Program Files\Python38\lib\site-packages\flask_sqlalchemy\__init__.py", line 1016, in _execute_for_all_tables
    app = self.get_app(app)
  File "C:\Program Files\Python38\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/.

错误 2

PS Python_Flask> & "C:/Program Files/Python38/python.exe" c:/Document/Codes/Python_Flask/run.py
C:\Program Files\Python38\lib\site-packages\flask_sqlalchemy\__init__.py:833: FSADeprecationWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future.  Set it to True or False to suppress this warning.
  warnings.warn(FSADeprecationWarning(
Traceback (most recent call last):
  File "c:/Document/Codes/Python_Flask/run.py", line 3, in <module>
    app = create_app()
  File "c:\Document\Codes\Python_Flask\flaskblog\__init__.py", line 54, in create_app
    db.create_all()
  File "C:\Program Files\Python38\lib\site-packages\flask_sqlalchemy\__init__.py", line 1039, in create_all
    self._execute_for_all_tables(app, bind, 'create_all')
  File "C:\Program Files\Python38\lib\site-packages\flask_sqlalchemy\__init__.py", line 1031, in _execute_for_all_tables
    op(bind=self.get_engine(app, bind), **extra)
  File "C:\Program Files\Python38\lib\site-packages\flask_sqlalchemy\__init__.py", line 962, in get_engine
    return connector.get_engine()
  File "C:\Program Files\Python38\lib\site-packages\flask_sqlalchemy\__init__.py", line 555, in get_engine
    options = self.get_options(sa_url, echo)
  File "C:\Program Files\Python38\lib\site-packages\flask_sqlalchemy\__init__.py", line 570, in get_options
    self._sa.apply_driver_hacks(self._app, sa_url, options)
  File "C:\Program Files\Python38\lib\site-packages\flask_sqlalchemy\__init__.py", line 883, in apply_driver_hacks
    if sa_url.drivername.startswith('mysql'):
AttributeError: 'NoneType' object has no attribute 'drivername'

Answer 1

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