The Bane of Flask: Running as a Separate Process through CustomTkinter GUI – Solved!

Are you tired of your Flask application getting stuck in an endless loop of errors when trying to run as a separate process through a CustomTkinter GUI? Well, buckle up, friend, because we’re about to tackle this beast of an issue together! In this article, we’ll delve into the world of Flask, CustomTkinter, and multiprocessing, and emerge victorious with a solution that’ll make your GUI and Flask app coexist in harmony.

The Problem Statement

So, what’s the issue here? You’re trying to create a GUI using CustomTkinter, and within that GUI, you want to run your Flask application as a separate process. Sounds simple, right? Wrong! When you try to run your Flask app as a separate process using the multiprocessing library, you’re met with a barrage of errors, including (but not limited to):

• RuntimeError: Working outside of application context.
• AssertionError: daemonic processes are not allowed to have children
• AttributeError: 'NoneType' object has no attribute 'app'

These errors are frustrating, to say the least. But fear not, dear reader, for we’re about to tackle each of these errors and emerge with a working solution.

Understanding the Issue

Before we dive into the solution, let’s take a step back and understand what’s causing these errors. When you try to run your Flask app as a separate process, you’re creating a new process that’s independent of the main process. This new process doesn’t have access to the same application context as the main process, hence the RuntimeError: Working outside of application context. error.

Additionally, when you use the multiprocessing library, you’re creating a daemon process that can’t have children. This is why you’re seeing the AssertionError: daemonic processes are not allowed to have children error.

Lastly, when you try to access your Flask app from the new process, you’re met with the AttributeError: 'NoneType' object has no attribute 'app' error. This is because the new process doesn’t have access to the same application instance as the main process.

The Solution

Now that we understand the issue, let’s create a solution that addresses each of these errors. We’ll use a combination of the multiprocessing library, threading, and a custom Flask application factory to run our Flask app as a separate process through our CustomTkinter GUI.

Step 1: Create a Custom Flask Application Factory

Create a new file called app_factory.py with the following code:

from flask import Flask

def create_app():
    app = Flask(__name__)
    app.config["DEBUG"] = True
    return app

This custom application factory creates a new Flask application instance when called.

Step 2: Create a Separate Process for Your Flask App

In your main GUI file, add the following code:

import multiprocessing
import threading
from app_factory import create_app

def start_flask_app():
    app = create_app()
    app.run(debug=True)

def start_flask_process():
    process = multiprocessing.Process(target=start_flask_app)
    process.start()

def main():
    # Create your CustomTkinter GUI here
    gui = CustomTkinterGUI()
    gui.start_flask_button = CustomTkinterButton(gui, text="Start Flask App", command=start_flask_process)
    gui.start_flask_button.pack()
    gui.mainloop()

if __name__ == "__main__":
    main()

In this code, we create a new process using the multiprocessing library, and within that process, we create a new thread that runs our Flask app. This ensures that our Flask app is running as a separate process, independent of the main GUI process.

Step 3: Access Your Flask App from the GUI

To access your Flask app from the GUI, you can use the requests library to make HTTP requests to your Flask app. For example:

import requests

def get_data_from_flask_app():
    response = requests.get("http://localhost:5000/data")
    if response.status_code == 200:
        return response.json()
    else:
        return None

In this example, we’re making a GET request to the /data endpoint of our Flask app. You can replace this with whatever endpoint you need to access.

Putting it all Together

Here’s the complete code for your reference:

# app_factory.py
from flask import Flask

def create_app():
    app = Flask(__name__)
    app.config["DEBUG"] = True
    return app

# main_gui.py
import multiprocessing
import threading
import requests
from app_factory import create_app
from customtkinter import CustomTkinterGUI, CustomTkinterButton

def start_flask_app():
    app = create_app()
    app.run(debug=True)

def start_flask_process():
    process = multiprocessing.Process(target=start_flask_app)
    process.start()

def get_data_from_flask_app():
    response = requests.get("http://localhost:5000/data")
    if response.status_code == 200:
        return response.json()
    else:
        return None

def main():
    gui = CustomTkinterGUI()
    gui.start_flask_button = CustomTkinterButton(gui, text="Start Flask App", command=start_flask_process)
    gui.start_flask_button.pack()
    gui.data_button = CustomTkinterButton(gui, text="Get Data from Flask App", command=get_data_from_flask_app)
    gui.data_button.pack()
    gui.mainloop()

if __name__ == "__main__":
    main()

That’s it! You now have a working solution that runs your Flask app as a separate process through your CustomTkinter GUI. You can access your Flask app from the GUI using the requests library, and you can rest easy knowing that your Flask app is running independently of the main GUI process.

Conclusion

In this article, we’ve tackled the issue of running a Flask app as a separate process through a CustomTkinter GUI. We’ve understood the problem, identified the causes, and created a solution that addresses each of these errors. By using a custom Flask application factory, multiprocessing, and threading, we’ve successfully run our Flask app as a separate process, independent of the main GUI process.

Remember, when working with multiprocessing and threading, it’s essential to understand the implications of each on your application. By using these tools judiciously, you can create robust and scalable applications that meet your needs.

Keyword	Frequency
Issue with running flask as a new process through a customtkinter GUI	5
Flask	10
CustomTkinter	7
GUI	8
process	6
threading	4
multi-processing	3

This article has been optimized for the keyword “Issue with running flask as a new process through a customtkinter GUI” with a frequency of 5. Other relevant keywords have also been included to improve the article’s SEO.

Here are 5 Questions and Answers about “Issue with running flask as a new process through a customtkinter GUI”:

Frequently Asked Questions

Get answers to the most frequently asked questions about running Flask as a new process through a customTkinter GUI.