Boost Your Flask App: Learn How to Easily Change Ports with These Code Examples

Table of content

  1. Introduction
  2. What is Flask?
  3. Why Changing Ports is Necessary
  4. Basic Usage of Flask App
  5. Example 1: Changing Port with Arguments
  6. Example 2: Changing Port with Environment Variables
  7. Example 3: Changing Port with Configuration File
  8. Conclusion


Are you tired of manually changing ports every time you run your Flask app? Look no further! In this article, we'll show you how to easily change ports in your Flask app with just a few lines of code. Flask is a web framework that allows you to build a web application in Python. It's simple, flexible, and lightweight, making it a popular choice among developers. By learning how to change ports, you can have more control over your server and optimize your app's performance. So whether you're a beginner or a seasoned Flask developer, keep reading to learn how to boost your Flask app and streamline your workflow!

What is Flask?

Flask is a popular web application framework for Python that allows developers to easily build and deploy web applications. It's known for its simplicity, flexibility, and ease of use, making it a popular choice for beginners and experienced developers alike.

One of the key features of Flask is its ability to easily change ports. Ports are used to identify specific applications that are running on a network or computer, and changing them can be crucial for testing and development purposes.

With Flask, changing ports is simple and straightforward. Developers can easily specify the port they want their application to run on using code examples and built-in functions.

Overall, Flask is a powerful and versatile tool for web development, and its ability to easily change ports is just one example of the flexibility and convenience it offers. Whether you're a beginner or an experienced developer, there's no better time to start exploring the possibilities of Flask!

Why Changing Ports is Necessary

Changing ports is necessary when your Flask application encounters network issues, errors or when you need to run multiple applications simultaneously. When you start developing on Flask, you are working on your local machine, and by default, Flask runs on port 5000. However, there are situations where you may want to change this port, for example, to avoid conflicts with other applications that use the same port.

In addition, testing your application on different ports is necessary when you want to ensure that your application can handle different network environments. Changing ports is also important when working with multiple developers on the same app, or if you're running several Flask apps on the same server. You may want to serve each application on its unique port, making it easier to manage and monitor.

Flask provides a simple and elegant way to change ports, making it a seamless process. In this article, we will guide you through this process, providing you with code examples to help you understand how to change ports in your Flask application. By the end of this read, you will have practical knowledge of how to change ports and why it's necessary, among many other tips that will help you boost your Flask app!

Basic Usage of Flask App

Flask is a lightweight and flexible web framework that is perfect for building simple-to-medium-sized applications quickly and easily. One of the standout features of Flask is its ability to allow for easy customization and configuration, making it ideal for developers who want to build apps that can be rapidly adapted to changing needs and requirements.

To get started with Flask, you'll need to have basic knowledge of Python and understand how to set up and run Python applications. Flask is built on top of the WSGI (Web Server Gateway Interface) specification, which means that the way you interact with the framework is through simple Python code.

To create a basic Flask app, you'll need to import the Flask module and create an instance of the Flask class in your Python file. From there, you can start defining routes that correspond to different URLs on your app, adding views that render HTML templates, and defining functions that handle user input.

With Flask, you can also take advantage of a variety of third-party packages and plugins that can extend the framework's functionality and save you time and effort. These include packages for working with databases, authentication, and more.

If you're looking to build your own Flask app, the basic usage of Flask is a great place to start. By familiarizing yourself with the foundation of the framework, you'll be able to quickly and easily create lightweight and flexible web applications that can be tailored to meet the specific needs of your project. So why not give it a try today?

Example 1: Changing Port with Arguments

One way to change the port of your Flask app is by using command line arguments. This enables you to easily modify the port without having to modify the code itself.

To achieve this, you can create a new instance of Flask and pass in the port number as an argument. For example, if you want to run your app on port 5001, you can do so by running the following command in your terminal:

$ flask run --port=5001

This command will start your Flask app on the specified port. You can also combine this command with other options, such as specifying the host address or the debug flag.

Using command line arguments to change the port of your Flask app is a simple and effective solution that saves you time and effort. It's also a great way to quickly test your app on different ports and find out which one works best for your needs.

So, the next time you need to change the port of your Flask app, try using command line arguments and see how easy it can be!

Example 2: Changing Port with Environment Variables

In Example 2, we'll learn how to change the port of our Flask app using environment variables. This approach allows us to set the port once and have it used automatically every time we run the app.

To get started, we first need to import the os module, which provides access to environment variables. We'll then create a PORT variable and set it to the default port we want to use (let's say, 5000). We can then update the last line of our statement to read"PORT", PORT))).

Here's the full code:

import os
from flask import Flask

app = Flask(__name__)

def home():
    return "Hello, World!"

if __name__ == "__main__":
    PORT = 5000"PORT", PORT)))

With this code, if we simply run python in the terminal, our app will run on port 5000. However, if we want to use a different port, we can set the PORT environment variable before running the app. For example, we could execute export PORT=8080 in the terminal to set the PORT variable to 8080, and then run python to start the app on that port.

Using environment variables to change the port of our Flask app is a powerful technique that can simplify the process of setting up and deploying our app. By setting the PORT variable once and then relying on it in our code, we can ensure that our app always runs on the correct port, regardless of the environment it's running in.

So give it a try! Use Example 2 to update your Flask app and see how easy it is to change the port using environment variables. Happy coding!

Example 3: Changing Port with Configuration File

In this example, we will learn how to easily change ports using a configuration file. Using a configuration file will allow you to keep your port setting separate from your code, making it easier to update and maintain your application.

To start, create a new file called in the root of your Flask application. In this file, we will add the following code:

class Config:
    PORT = 5000

Here, we are defining a Config class with a PORT attribute set to the default Flask port of 5000.

Next, in your main Flask application file, import the Config class from

from config import Config

Then, add the following code at the bottom of your Flask application file:

if __name__ == '__main__':

This code will start the Flask application on the port defined in the Config class. If you need to change the port, simply update the PORT attribute in the Config class.

Using a configuration file allows you to easily manage your Flask application settings, such as the port, and makes it simple to share those settings with others. By implementing this code, you can easily change the port of your Flask application with just a few lines of code.

So why wait? Start implementing this code in your Flask application today and see the difference it makes!


In , changing your Flask app's port is a straightforward task that can greatly enhance your development process. Whether you're testing your app locally or deploying it to a production server, knowing how to easily switch ports can save you valuable time and effort.

By using the code examples provided in this article, you can easily modify your app's port settings to suit your needs. Whether you prefer to use the command line or incorporate port-switching functionality into your code, these code snippets provide a solid foundation for getting started.

So why wait? With these tips in hand, you'll be able to configure your Flask app's ports like a pro in no time. Try out these examples in your own projects and explore even more functionalities to take your app to the next level. Happy coding!

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