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Python circular import error with flask and celery

How can I make #celery.task available on user resources package?
I'm new to python and confused about the "circular imports error" can somebody explain how it works? and how to handle this kind of errors in flask application. This is the part where I always get stuck.
This is my project current folder structure
code
|_resources
| |_user.py
|
|_utils
| |_flask_celery.py
|
|_flask_app.py
--- SOURCE CODE ---
flask_app.py
from flask import Flask
from flask_cors import CORS
from flask_restful import Api
from util.flask_celery import make_celery
from routes.endpoint import urls
from resources.user import Users
app = Flask(__name__)
CORS(app, resources={r"/*": {"origins": "*"}})
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql:///username:StrongPassword#localhost:3306/db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['CELERY_BROKER_URL'] = 'amqp//admin:StrongPassword#localhost:5672'
app.config['CELERY_RESULT_BACKEND'] = 'db+mysql:///username:StrongPassword#localhost:3306/db'
app.config['PROPAGATE_EXCEPTIONS'] = True
api = Api(app)
celery = make_celery(app)
url = urls()
api.add_resource(Users, url.get('users'))
if __name__ == "__main__":
# sqlalchemy
from db import db
db.__init__(app)
app.run(host='0.0.0.0', debug=True, port=5000)
flask_celery.py
from celery import Celery
def make_celery(celery_app):
celery = Celery(
celery_app.import_name,
backend=celery_app.config['CELERY_RESULT_BACKEND'],
broker=celery_app.config['CELERY_BROKER_URL']
)
celery.conf.update(celery_app.config)
class ContextTask(celery.Task):
def __call__(self, *args, **kwargs):
with celery_app.app_context():
return self.run(*args, **kwargs)
celery.Task = ContextTask
return celery
user.py
from flask_restful import Resource, reqparse
from app import celery # <-- this cause the error
from util.zk_connector import zk_connect
from util.zk_error import error
class Users(Resource):
def post(self, ip, comkey):
zk = zk_connect(ip=ip, password=int(comkey))
try:
session = zk.connect()
session.disable_device()
users = session.get_users()
print(users)
session.enable_device()
session.disconnect()
return {'message': 'success'}, 200
except Exception as e:
return error(e)
#celery.task(name='user.reverse')
def reverse(string):
return string[::-1]
Error:
Traceback (most recent call last):
File ".\flask_app.py", line 6, in <module>
from resources.user import User
File "C:\Users\Gelo\Documents\Brand new clean arch pyzk\code\resources\user.py", line 2, in <module>
from flask_app import celery
File "C:\Users\Gelo\Documents\Brand new clean arch pyzk\code\flask_app.py", line 6, in <module>
from resources.user import User
ImportError: cannot import name 'User' from partially initialized module 'resources.user' (most likely due to a circular import) (C:\Users\Gelo\Documents\Brand new clean arch pyzk\code\resources\user.py)

"flask.cli.NoAppException" while running flask app

I am fairly new to python development and have no idea about flask, I have been assigned a project that is developed using flask. After working for couple of weeks i am now able to resolve all the dependencies and project is now compiled successfully. But when I run the project using flask run and then enter the url in browser it throws "flask.cli.NoAppException". How can I run my project I have tried like this.
set FLASK_APP=init.py
set FLASK_ENV=develpment
flask run
Serving Flask app "init.py" (lazy loading)
Environment: develpment
Debug mode: on
Restarting with stat
Debugger is active!
Debugger PIN: 202-733-235
Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
here is the trackback
"FLASK_APP=myappnam:name to specify one.
Traceback (most recent call last)
File "C:\Program Files\Python38\Lib\site-packages\flask\_compat.py", line 39, in reraise
raise value
File "C:\Program Files\Python38\Lib\site-packages\flask\cli.py", line 97, in find_best_app
raise NoAppException(
flask.cli.NoAppException: Failed to find Flask application or factory in module "myappnam". Use "FLASK_APP=myappnam:name to specify one.
The debugger caught an exception in your WSGI application. You can now look at the traceback which led to the error.
To switch between the interactive traceback and the plaintext one, you can click on the "Traceback" headline. From the text traceback you can also create a paste of it. For code execution mouse-over the frame you want to debug and click on the console icon on the right side.
You can execute arbitrary Python code in the stack frames and there are some extra helpers available for introspection:
dump() shows all variables in the frame
dump(obj) dumps all that's known about the object
here is my --init--.py file
import os
import logging
import gevent
import datetime
import rollbar
from gevent.queue import Queue
from gevent.event import AsyncResult
import zmq.green as zmq
from werkzeug.contrib.fixers import ProxyFix
# Greens the postgress connector
try:
import psycogreen.gevent
psycogreen.gevent.patch_psycopg()
except ImportError:
pass
from rauth.service import OAuth2Service
from flask import Flask, Request
from flask_sqlalchemy import SQLAlchemy
from flask_bcrypt import Bcrypt
from flask_login import LoginManager, current_user
from flask_assets import Environment
from flask_uploads import UploadSet, configure_uploads, IMAGES
from app.util import setup_logging
from app.exceptions import TimeoutError, BackendError
import app.exceptions
flask_app = None
# Have to use an actor pattern because we cannot allow more than one request to
# be pending at a time.
class Backend(gevent.Greenlet):
def __init__(self):
super(Backend, self).__init__()
self.inbox = Queue()
self.zmq_context = zmq.Context()
self.zmq_socket = None
self.init_socket()
def init_socket(self):
zmq_socket = self.zmq_socket
if zmq_socket is not None:
zmq_socket.close(0)
zmq_socket = self.zmq_context.socket(zmq.REQ)
zmq_socket.connect(flask_app.config["SERVER_ZMQ_URI"])
self.zmq_socket = zmq_socket
def process(self, request):
zmq_socket = self.zmq_socket
poller = zmq.Poller()
poller.register(zmq_socket, zmq.POLLIN)
zmq_socket.send_json({
"command": request["command"],
"arguments": request["arguments"]
})
sockets = dict(poller.poll(10 * 1000))
if zmq_socket not in sockets:
self.init_socket()
result = request["result"]
result.set_exception(TimeoutError("The request to the backend timed out."))
return
received = zmq_socket.recv_json()
result = request["result"]
if received["success"]:
result.set(received["result"])
else:
result.set_exception(BackendError(received["result"]))
def _run(self):
while True:
self.process(self.inbox.get())
def send(self, command, **kwargs):
result = AsyncResult()
self.inbox.put({
"command": command,
"arguments": kwargs,
"result": result
})
return result.get()
class RollbarRequest(Request):
#property
def rollbar_person(self):
if current_user.is_anonymous:
return {
"id": 0,
"username": "anonymous"
}
return {
"id": current_user.id,
"username": current_user.name,
"email": current_user.email_address
}
def create_app(*args, **kwargs):
global flask_app
global l
app_mode = os.environ.get("APP_MODE")
assert app_mode is not None, "APP_MODE environment variable must be set"
flask_app = Flask(__name__)
flask_app.request_class = RollbarRequest
flask_app.config.from_object("config.mode_{}".format(app_mode))
flask_app.config["APP_MODE"] = app_mode
setup_logging(flask_app.config["LOGGING_LEVEL"])
l = logging.getLogger(__name__)
l.info("starting in mode {}".format(app_mode))
if not flask_app.config["DEBUG"]:
rollbar.init(
flask_app.config["ROLLBAR_API_KEY"],
app_mode,
allow_logging_basic_config=False
)
flask_app.jinja_env.globals.update(
current_year=lambda: datetime.datetime.now().year
)
# Have to do this so that redirects work in proxy mode behind NGINX.
if not flask_app.debug:
flask_app.wsgi_app = ProxyFix(flask_app.wsgi_app)
flask_app.db = SQLAlchemy(flask_app)
flask_app.bcrypt = Bcrypt(flask_app)
flask_app.assets = Environment(flask_app)
flask_app.images = UploadSet("images", IMAGES)
configure_uploads(flask_app, flask_app.images)
flask_app.photos = UploadSet("photos", IMAGES)
configure_uploads(flask_app, flask_app.photos)
login_manager = LoginManager()
login_manager.login_view = "signin"
login_manager.login_message_category = "alert" # Need newer release of Flask-Login for this to work.
login_manager.init_app(flask_app)
flask_app.facebook = OAuth2Service(
name="facebook",
base_url="https://graph.facebook.com/v2.8/",
client_id=flask_app.config["FACEBOOK_CLIENT_ID"],
client_secret=flask_app.config["FACEBOOK_CLIENT_SECRET"]
)
from app import views
from app import models
from app import commands
flask_app.backend = Backend()
flask_app.backend.start()
app.exceptions.register(flask_app)
return flask_app
and this is my project structure
I am using pycharm and widows 10.

In your create_app function you probably do not want to use the global keyword for late initialisation of the app.
In the examples you provided the create_app function is never called, and so the app instance is never created. It is more common to use the create_app function as follows:
def create_app():
app = flask.Flask(__name__)
# do some setup
return app
app = create_app()
The app instance should also be called app and not flask_app. Of course you can call it whatever you want, but by default flask looks for app. To specify your own change FLASK_APP=__init__.py to FLASK_APP=__init__:flask_app

Python Flask factory application problem with Flask-Mqtt has no attribute 'init_app'

I struggle with the implementation of the Flask-MQTT lib to my app. SQLAlchemy etc works fine, but
flask-mqtt throws the error AttributeError: module 'app.mqtt' has no attribute 'init_app'.
In the offical documentatio of Flask-MQTT they build up the create_app() Method the same way
( https://flask-mqtt.readthedocs.io/en/latest/usage.html )
Would be greate if someone can help me! Thank you very much
__init__.py
from flask import Flask
from flask_restful import Api
from flask_mqtt import Mqtt
from flask_sqlalchemy import SQLAlchemy
from flask_marshmallow import Marshmallow
from flask_jwt_extended import JWTManager
mqtt = Mqtt()
api = Api()
db = SQLAlchemy()
ma = Marshmallow()
jwt = JWTManager()
def create_app(config):
app = Flask(__name__)
app.config.from_object(config.DevelopmentConfig)
mqtt.init_app(app)
db.init_app(app)
api.init_app(app)
ma.init_app(app)
jwt.init_app(app)
return app
from app.mqtt import mqttclient
run.py
from app import create_app
import config
from flask_migrate import Migrate
app = create_app(config)
migrate = Migrate(app, db)
app.config['MQTT_BROKER_URL'] = 'hivemq'
app.config['MQTT_BROKER_PORT'] = 1883
app.config['MQTT_USERNAME'] = ''
app.config['MQTT_PASSWORD'] = ''
app.config['MQTT_KEEPALIVE'] = 5
app.config['MQTT_TLS_ENABLED'] = False
if __name__ == '__main__':
app.run(host='0.0.0.0', port=5003, threaded=True)
ERROR:
mqttservice | Traceback (most recent call last):
mqttservice | File "run.py", line 5, in <module>
mqttservice | app = create_app(config)
mqttservice | File "/code/app/__init__.py", line 18, in create_app
mqttservice | mqtt.init_app(app)
mqttservice | AttributeError: module 'app.mqtt' has no attribute 'init_app'

In that code fragment, mqtt has two meanings. The first is the variable assigned in
mqtt = Mqtt()
The second is a namespace (module)
from app.mqtt import mqttclient
The tell is in the error
AttributeError: module 'app.mqtt' has no attribute 'init_app'
which is happening because the import is overwriting the initial value, so by the time of that .init_app(), mqtt isn't what you expected.
You're going to have to change one of those names.

Flask ImportError: cannot import name routes

I'm converting a cli application to use a REST api and I've read up on flask and I thought I understood things but apparently not :-D. based on this: https://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-i-hello-world
I have a directory structure:
--myApp
myApp.py
--APIService
__init__.py
WebService.py
myApp.py:
from APIService import app
app.run(debug = True )
init:
from flask import Flask
app = Flask(__name__)
from app import routes
WebService.py:
from APIService import app
class WebService(object):
'''
classdocs
'''
def __init__(self,):
'''
Constructor
'''
#app.route('/')
#app.route('/index')
def index():
return "Hello, World!"
I've tried this a few different ways like renaming app to APIService but I keep circling back to the same error: APIService\__init__.py", line 5, in <module> from app import routes ImportError: No module named app
I just don't get what I'm doing wrong here. I did pip install flask so the module is there. I skipped the environment part but that's because I wasn't bothered with running globally for now. anyone have a clue as to what I messed up?

In the following line insideAPIService\__init__.py:
from app import routes
the keyword routes is referencing a separate Python Module inside the APIService folder that is named "routes.py" in the Flask Mega Tutorial. It seems like you have renamed the "routes.py" file to "WebService.py" so you can solve the import issue by changing the import line insideAPIService\__init__.pyto:
from app import WebService

Flask ImportError: cannot import name 'app' [duplicate]

Trying to run my python file updater.py to SSH to a server and run some commands every few set intervals or so. I'm using APScheduler to run the function update_printer() from __init__.py. Initially I got a working outside of application context error but someone suggested that I just import app from __init__.py. However it isn't working out so well. I keep getting a cannot import name 'app' error.
app.py
from queue_app import app
if __name__ == '__main__':
app.run(debug=True)
__init__.py
from flask import Flask, render_template
from apscheduler.schedulers.background import BackgroundScheduler
from queue_app.updater import update_printer
app = Flask(__name__)
app.config.from_object('config')
#app.before_first_request
def init():
sched = BackgroundScheduler()
sched.start()
sched.add_job(update_printer, 'interval', seconds=10)
#app.route('/')
def index():
return render_template('index.html')
updater.py
import paramiko
import json
from queue_app import app
def update_printer():
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(app.config['SSH_SERVER'], username = app.config['SSH_USERNAME'], password = app.config['SSH_PASSWORD'])
...
File Structure
queue/
app.py
config.py
queue_app/
__init__.py
updater.py
Error
Traceback (most recent call last):
File "app.py", line 1, in <module>
from queue_app import app
File "/Users/name/queue/queue_app/__init__.py", line 3, in <module>
from queue_app.updater import update_printer
File "/Users/name/queue/queue_app/updater.py", line 3, in <module>
from queue_app import app
ImportError: cannot import name 'app'
What do I need to do be able to get to the app.config from updater.py and avoid a "working outside of application context error" if ran from APScheduler?

It's a circular dependency, as you import updater in your __init__.py file. In my Flask setup, app is created in app.py.