lask.cli.NoAppException: While importing "app", an ImportError was raised:

Question

1.I'm trying to build a flask project and try to import the class into models.py and import routes into app.py. When I was trying to run the project, it showed some errors. Here is the information for traceback:

Traceback (most recent call last):
  File "/Users/cheliang/Desktop/project/env/lib/python3.8/site-packages/flask/cli.py", line 240, in locate_app
    __import__(module_name)
  File "/Users/cheliang/Desktop/project/app.py", line 4, in <module>
    from user import routes
  File "/Users/cheliang/Desktop/project/user/routes.py", line 1, in <module>
    from user.models import User
ImportError: cannot import name 'User' from 'user.models' (/Users/cheliang/Desktop/project/user/models.py)

The tree structure for my project:

├── app.py
├── env
── run
├── static
│   ├── css
│   │   ├── normalize.css
│   │   └── styles.css
│   └── js
│       ├── jquery.js
│       └── scripts.js
├── templates
│   ├── base.html
│   ├── dashboard.html
│   └── home.html
└── user
    ├── __init__.py
    ├── __pycache__
    │   ├── __init__.cpython-38.pyc
    │   ├── models.cpython-38.pyc
    │   └── routes.cpython-38.pyc
    ├── models.py
    └── routes.py

2.Here is the code details: models.py:

from flask import Flask, jsonify
class User:
    def signup(self):

        user = {
         "_id":"",

         "name":"",
         "email":"",
         "password":""

        }
        return jsonify(user),200

Here is the routes.py:

from user.models import User
from flask import Flask
from app import app 

@app.route('/user',methods=["GET"])
def signup(self):
    return User().signup()

Here is the code for app.py

from flask import Flask ,render_template

app = Flask(__name__)
from user import routes

@app.route('/')
def home():
    return render_template('home.html')

@app.route('/dashboard')
def dashboard():
    return render_template('dashboard.html')

Answer 1

For a minimalist flask application, consider this kind of structure:

project_folder
    |---------- app.py
    |---------- config.py
    |---------- .env
    |---------- requirements.txt
    |---------- .flaskenv
    |---------- app/
                  |------ routes.py
                  |------ models.py
                  |------ __init__.py
                  |------ forms.py
                  |------ templates/
                              |-------- home.html
                              |-------- base.html
                              |-------- dashbooard.html
                  |------ static/
                            |-------css/
                                     |------- styles.css
                                     |------- normalize.css
                            |-------js/
                                     |------- jquery.js
                                     |------- scripts.js

Create application instance:

# __init__.py

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
db = SQLAlchemy(app)

from app import routes, models

Working with flask models:

# models.py

from app import db

class User(object):
    username = db.Column(db.String())
    # ...

# routes.py

from flask import render_template
from app import app 
from app.models import User
from app.forms import <your-form>

@app.route('/')
def home():
    return render_template('home.html')

@app.route('/dashboard')
def dashboard():
    return render_template('dashboard.html')

@app.route('/user',methods=["GET"])
def signup():
    # ...
    user = User.query.filter_by(username=form.username.data)

Finally, create an entry point to your flask application in the app.py:

from app import app