FLASK SQLALCHEMY create_all() not working

Question

I know there is a typical question, but what am I doing wrong?
After set

FLASK_APP='safecanyons:app'
flask run

the application starts but no one table is created. This is the main script:

from flask import Flask, request, jsonify, g
from flask_sqlalchemy import SQLAlchemy
from flask_jwt_extended import JWTManager, jwt_required
from safecanyons.models.users import User
from safecanyons.v1.users import bp as bp_users
from safecanyons.settings.dev import SQLALCHEMY_DATABASE_URI
from psycopg2 import connect
from flask_sqlalchemy import SQLAlchemy
from safecanyons.models.users import User

def create_app():
    # The imports :
    # from safecanyons.settings.dev import SQLALCHEMY_DATABASE_URI
    
    # SQLALCHEMY_DATABASE_URI = "postgresql://{}:{}@{}/{}".format(
    # DB_USER, DB_PASSWORD, DB_HOST,DB_NAME
    # ) 
    # 
    # from safecanyons.models.users import User
    # 
    # from flask_sqlalchemy import SQLAlchemy
    # db = SQLAlchemy()

    # class User(db.Model):
    # __tablename__ = 'users'
    
    # id = db.Column(db.Integer, primary_key=True)
    # username = db.Column(db.String(80), unique=True, nullable=False)
    # email = db.Column(db.String(120), unique=True, nullable=False)

    # def __repr__(self):
    #     return '<User %r>' % self.username
      
    uri = SQLALCHEMY_DATABASE_URI
    app = Flask('safecanyons')
    app.config['SQLALCHEMY_DATABASE_URI'] = uri
    SQLALCHEMY_TRACK_MODIFICATIONS = True
    db = SQLAlchemy(app)
    from safecanyons.models.users import User

    db.create_all()
  
    jwt = JWTManager(app)
    app.register_blueprint(bp_users,url_prefix='/v1/users')
    return app,db

app,db = create_app()


@app.route("/")
def hello_world():
    return "<p>Hello, World!</p>"

I've tried with the app.app_context() but it doesn't work as I expect. When I go to database to check the users table creation, no one table exists.

But when you execute db.create_all()? You must do it explicitly. — jorzel
– jorzel, Commented Dec 10, 2021 at 7:28
When I run flask I do: export FLASK_APP=‘safecanyons:app’ so I think create_app() is called then. Also after your comment I’ve tried to call manually after flask run was raised an also still not working(not creating the models) — Javier
– Javier, Commented Dec 10, 2021 at 17:54
Are you sure that User model definition is imported before create_all(). Becuaeu you have import but also commented code. You can try to put User — jorzel
– jorzel, Commented Dec 10, 2021 at 18:09

Ortomala Lokni · Accepted Answer · 2023-03-25 08:24:04Z

You probably have problems with importing User model in the right way (because when using create_app pattern there is circular import challange, and you are doing strange hack with returning db from create_app). User must be defined before create_all call, but User to be defined need db but also create_all need. How to solve it (I may be wrong with file names and project structure):

safecanyons/app.py

from flask_jwt_extended import JWTManager, jwt_required
from flask_sqlalchemy import SQLAlchemy
from psycopg2 import connect

from safecanyons.v1.users import bp as bp_users
from safecanyons.settings.dev import SQLALCHEMY_DATABASE_URI


db = SQLAlchemy()

def create_app():
    from safecanyons.models.users import User
 
    uri = SQLALCHEMY_DATABASE_URI
    app = Flask('safecanyons')
    app.config['SQLALCHEMY_DATABASE_URI'] = uri
    SQLALCHEMY_TRACK_MODIFICATIONS = True

    db.init_app(app) # init of db is deferred
    db.create_all()

    jwt = JWTManager(app)
    app.register_blueprint(bp_users,url_prefix='/v1/users')
    return app
   
app = create_app()

@app.route("/")
def hello_world():
    return "<p>Hello, World!</p>"

safecanyons/models/users.py:

from safecayons.app import db

class User(db.Model):
    __tablename__ = 'users'
    
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True, nullable=False)
    email = db.Column(db.String(120), unique=True, nullable=False)

    def __repr__(self):
        return '<User %r>' % self.username

The other solution is place above code in one file, but model User should be defined before create_all call.

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