python - 如何从 __init__.py 导入应用程序以及为什么会出现此错误？

Question

我要导入 db来自 __init__.py在 model.py文件，但我无法导入，出现错误提示:

Traceback (most recent call last):
  File "/home/rohit/Desktop/flask_app/run.py", line 1, in <module>
    from bytewar import create_app
  File "/home/rohit/Desktop/flask_app/bytewar/__init__.py", line 5, in <module>
    from bytewar.user.views import user_blueprint
  File "/home/rohit/Desktop/flask_app/bytewar/user/views.py", line 9, in <module>
    from bytewar.model import Login_form, Login, Post, Contacts, Signup_form, Contacts
  File "/home/rohit/Desktop/flask_app/bytewar/model.py", line 5, in <module>
    from bytewar import db
ImportError: cannot import name 'db'

我的应用程序树:

___ run.py     # <<------- ImportError in this file.
___ bytewar/
  |__ __init__.py
  |__ config.py
  |__ model.py       
  |__ user/
  |   |__ __init__.py
  |   |__ views.py
  |   |__ static/
  |   |    |__ img/
  |   |    |__ ....
  |   |__ template/
  |       |__ index.html
  |       |__ about.html
  |
  |__ admin/
      |__ __init__.py
      |__ views.py
      |__ template/
          |__ index.html
          |__ about.html

__init__.py:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_bootstrap import Bootstrap 
from flask_login import LoginManager
from bytewar.user.views import user_blueprint
from bytewar.admin.views import admin_blueprint

db = SQLAlchemy()

def create_app():
    app = Flask('bytewar')
    app = Flask(__name__.split('.')[0])
    app.config.from_pyfile('config.py')
    app.config['DEBUG'] = True

    app.register_blueprint(user_blueprint)
    app.register_blueprint(admin_blueprint)

    login_manager = LoginManager()
    bootstrap = Bootstrap(app)

    db.init_app(app)
    login_manager.init_app(app)
    login_manager.session_protection = 'strong'

    return app

在这里你可以看到我 db.init_app(app)但我仍然收到 ImportError .

添加后 __init__.py bytewar.user/ 内的文件和 bytewar.admin/ (在 views.py 旁边)，我在 run.py 中遇到错误:

Traceback (most recent call last):
  File "/home/rohit/Desktop/flask_app/run.py", line 1, in <module>
    from bytewar import app
  File "/home/rohit/Desktop/flask_app/bytewar/__init__.py", line 5, in <module>
    from bytewar.user.views import user_blueprint
  File "/home/rohit/Desktop/flask_app/bytewar/user/views.py", line 9, in <module>
    from bytewar.model import Login_form, Login, Post, Contacts, Signup_form, Contacts
  File "/home/rohit/Desktop/flask_app/bytewar/model.py", line 5, in <module>
    from run import db
  File "/home/rohit/Desktop/flask_app/run.py", line 1, in <module>
    from bytewar import app
ImportError: cannot import name 'app'

运行.py:

from bytewar import app


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

我的 bytewar/user/__init__.py原样 bytewar/admin/__int__.py :

from flask import Blueprint

user_blueprint = Blueprint(
    'user', __name__,
    static_folder='static',
    template_folder='template',
 )

为什么会这样？

Answer 1

在 bytewar.user.views你从你的 __init__.py 导入数据库.然而，这仅在导入下方定义了几行。所以在导入完成时， db 还不存在，错误确认了这一点。当你查看应用工厂的示例代码时1你看到app变量仅在定义后使用，您的代码也应该这样做。将您的导入移动到底部并设置好。

顺便说一句:你为​​什么要创建你的 app在工厂并立即覆盖它？留下第二个创作。