Application Factory Initialization Issues in Python Flask SQLAlchemy Blueprint

Question

I have issues with initialization with Application Factory. I am using Blueprint and SQLAlchemy. Here is my program structure.

App_v1
 app.py
 config.py
 App_Py
       main
           __init__.py
           forms.py
           views.py
       static
       templates
       __init__.py
      app_v1.db
      models.py

app.py

from App_Py import create_app
app=create_app()

if __name__=='__main__':
app.run(debug=True,port=4044)

config.py

import os
basedir = os.path.abspath(os.path.dirname(__file__))

class Config(object):
SECRET_KEY = ‘wdsfqsqdsqsdfqsqsdsq’
SQLALCHEMY_DATABASE_URI = 'sqlite:///'+os.path.join(basedir,'app_v1.db')
SQLALCHEMY_TRACK_MODIFICATIONS = False

App_Py init.py

import os
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
from flask_login import LoginManager
from config import Config

db = SQLAlchemy()
migrate=Migrate()
login_manager = LoginManager()
login_manager.login_view = 'users.login'

def create_app(config_class=Config):
  app = Flask(__name__)
  app.config.from_object(config_class)

  db.init_app(app)
  migrate.init_app(app, db)
  login_manager.init_app(app)

  from App_Py.main.views import main
  app.register_blueprint(main)
  return app

models.py

from App_Py import db,login_manager
from werkzeug.security import generate_password_hash,check_password_hash
from flask_login import UserMixin

class User(db.Model,UserMixin):

__tablename__ = 'users'

id = db.Column(db.Integer,primary_key=True)
email = db.Column(db.String(64),unique=True,index=True)
username = db.Column(db.String(64),unique=True,index=True)
password_hash = db.Column(db.String(128))

def __init__(self, email, username, password):
    self.email = email
    self.username = username
    self.password_hash = generate_password_hash(password)

def __repr__(self):
    return f"Username {self.username}"

class Task_Add(db.Model):

  id = db.Column(db.Integer,primary_key=True)
  task_add = db.Column(db.String(64))
  def __init__(self,task_add):
    self.task_add = task_add

  def __repr__(self):
    return f"{self.task_add}"

Inside main folder views.py

from flask import render_template,url_for,flash,redirect,request,Blueprint
from flask_login import current_user,login_required
from App_Py import db
from App_Py.main.forms import TaskForm
from App_Py.models import User,Task_Add

main = Blueprint('main',__name__)  

@main.route('/view_task’)
def view_task():

When I run the program, I cannot commit to create a user database while hitting Python in the command prompt:

from App_Py import db
from App_Py.models import User

u= User(username=‘dqfq’,email=‘one@one.com’,password=‘test’)
db.session.add(u)
db.session.commit()

when commit there is an error saying that cannot be commited. How to initalize Application Factory in Flask. The reason I am using application factory is I am going to use elastic search for later purposes. Thank you for your suggestions.

Error:

(venv) iMac:App_Py_v1 symtech$ python
Python 3.6.4 (v3.6.4:d48ecebad5, Dec 18 2017, 21:07:28) 
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from App_Py import db
>>> from App_Py.models import User
>>> u=User(username='David',email='david@gmail.com',password='test')
>>> db.session.add(u)
Traceback (most recent call last):
File "/Users/symtech/Desktop/App_Py/App_Py_v1/venv/lib/python3.6/site-     packages/sqlalchemy/util/_collections.py", line 999, in __call__
return self.registry[key]
KeyError: 4320752448

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Users/symtech/Desktop/App_Py/App_Py_v1/venv/lib/python3.6/site-   packages/sqlalchemy/orm/scoping.py", line 153, in do
return getattr(self.registry(), name)(*args, **kwargs)
File "/Users/symtech/Desktop/App_Py/App_Py_v1/venv/lib/python3.6/site-   packages/sqlalchemy/util/_collections.py", line 1001, in __call__
return self.registry.setdefault(key, self.createfunc())
File "/Users/symtech/Desktop/App_Py/App_Py_v1/venv/lib/python3.6/site- packages/sqlalchemy/orm/session.py", line 2950, in __call__
return self.class_(**local_kw)
File "/Users/symtech/Desktop/App_Py/App_Py_v1/venv/lib/python3.6/site-packages/flask_sqlalchemy/__init__.py", line 141, in __init__
self.app = app = db.get_app()
File "/Users/symtech/Desktop/App_Py/App_Py_v1/venv/lib/python3.6/site- packages/flask_sqlalchemy/__init__.py", line 912, in get_app
'No application found. Either work inside a view function or push'
RuntimeError: No application found. Either work inside a view function or    push an application context. See http://flask-sqlalchemy.pocoo.org/contexts/.
>>> >>>

Same issues and error occurs after changing:

def create_app(config_class=Config):
app = Flask(__name__)
app.config.from_object(config_class)

with app.app_context():
  db.init_app(app)
  migrate.init_app(app, db)
  ...........

  from APP_Py.users.views import users
  app.register_blueprint(users)
  ......

  return app

please provide complete error message from running in debug mode? — gittert, Oct 03 '18 at 08:54
I have posted the error. I cannot figure it out the problem? — Maxiom, Oct 03 '18 at 22:20
The issue seems to happen at commit function. Check this for possible solution, based on the error message. https://stackoverflow.com/questions/46540664/no-application-found-either-work-inside-a-view-function-or-push-an-application — gittert, Oct 04 '18 at 20:06
By changing with app.app_context(), the error still exists the same. — Maxiom, Oct 05 '18 at 00:59
can you add this to your question in code field? I cannot see what indentation you are using. — gittert, Oct 05 '18 at 10:08
I'll try and test this later today. Are you sure the indentation in your question is correct? I already spotted at least 1 issue in your function. — gittert, Oct 10 '18 at 06:39

score 0 · Answer 1 · answered Oct 10 '18 at 13:59

I noticed (just now) that you are trying to commit a user from command line. You might be missing any app context for committing to db. See the following url for solutions about adding users from command line: http://flask-sqlalchemy.pocoo.org/2.3/contexts/

Another solution I'm currently using in an app I'm working on is by adding the following in your main.py or even in create_app function should work.

    from App_Py import db
    from App_Py.models import User

    @app.before_first_request
    def load_user():
        u=User(username='David',email='david@gmail.com',password='test')
        db.session.add(u)
        db.session.commit()

Application Factory Initialization Issues in Python Flask SQLAlchemy Blueprint

1 Answers1