Why am I encountering an error while trying to run Flask on Python Visual Studio Code?

What will you learn?

In this tutorial, you will learn how to troubleshoot and resolve errors that occur when attempting to run Flask on Python Visual Studio Code.

Introduction to the Problem and Solution

Running Flask on Python Visual Studio Code can lead to errors due to various reasons such as incorrect configurations or missing dependencies. To overcome these challenges, it is crucial to identify the root cause of the error and apply appropriate solutions systematically. By following a structured approach, you can successfully execute Flask applications on Python Visual Studio Code without encountering any errors.


# Import necessary modules for Flask application
from flask import Flask

# Create a Flask app
app = Flask(__name__)

def hello_world():
    return 'Hello, World!'

if __name__ == '__main__':

# Copyright PHD


  • Importing Modules: We import the necessary Flask module from the flask package.
  • Creating App: A new instance of the Flask class named app is created.
  • Defining Route: The route / is defined to return ‘Hello, World!’ when accessed.
  • Running App: The script checks if it is executed directly and then runs the Flask application using app.run().
    How do I install Flask in my Python environment?

    To install Flask in your Python environment, you can use pip with the command:

    pip install flask
    # Copyright PHD

    Why am I getting an ImportError for ‘flask’ module?

    This error occurs when either you haven’t installed Flask in your environment or there are issues with your installation. Ensure that you have installed it correctly using pip.

    What should I do if my server fails to start with “Address already in use” error?

    This error usually occurs when another process is already using the same port number. You can try changing the port number by specifying it explicitly like: app.run(port=5001).

    How can I debug my Flask application in VSCode?

    You can set breakpoints in your code and use VSCode’s debugger feature by creating a launch configuration specific for debugging your Flask application.

    What does “ModuleNotFoundError: No module named ‘werkzeug'” mean?

    This means that Werkzeug, one of the dependencies of Flask, is not installed in your environment. Install Werkzeug using pip: pip install Werkzeug.

    How often does one need to restart their development server while working on a flask project locally?

    Whenever changes are made within main python files such as adding new routes etc., developers may need restarting their local development servers so that these changes take effect.


    Encountering errors while setting up and running a simple Flask program is common, especially for beginners. It’s essential to ensure all required libraries are properly installed and configured before proceeding. Understanding fundamental concepts around web frameworks, such as routes & views and middleware, can be beneficial for smoother development experiences.

    Leave a Comment