Unlock the Power of Heroku: How to Add Environment Variables with These Simple Code Examples

Table of content

  1. Introduction
  2. What are Environment Variables?
  3. Why are Environment Variables important in Heroku?
  4. How to add Environment Variables in Heroku:
  5. Method 1: Using the Heroku Dashboard
  6. Method 2: Using the Heroku CLI
  7. Method 3: Adding Environment Variables programmatically
  8. Example 1: Adding Environment Variables in a Node.js app
  9. Example 2: Adding Environment Variables in a Python app
  10. Example 3: Adding Environment Variables in a Ruby app
  11. Conclusion and Further Reading


Are you ready to take your Heroku development to the next level? Adding environment variables can unlock a world of possibilities, from fine-tuned application configuration to increased security. In this guide, we'll explore some simple code examples that will help you add environment variables to your Heroku app with ease.

Before we dive in, it's important to have a basic understanding of what environment variables are and why they are useful. Simply put, environment variables are variables that can be accessed by your application code that are set outside of the code itself. This means you can store sensitive information, such as API keys and other secrets, in a secure location without worrying about them being exposed in your codebase.

So, if you're ready to add some power to your Heroku apps, just follow along with these simple code examples and unlock the full potential of environment variables!

What are Environment Variables?

Environment variables are values that are accessible to a program running on a computer system. Think of them as information that is stored in the background of your system and can be accessed by programs when needed. Environment variables can store any type of data, including strings, integers, and Boolean values.

Environment variables have a wide range of uses. One common use is to store configuration data that is specific to an application. For example, if you have a Python application that connects to a database, you may store the database credentials as environment variables. This makes it easier to update the credentials without modifying the source code.

Another use of environment variables is to store system-level information. For instance, the PATH environment variable stores a list of directories that the system uses to find executable files. When you type a command in the terminal, the system looks for the binary file in the directories specified in PATH.

In summary, environment variables are a useful tool for programmers that allow applications to access system-level information or configuration data specific to a program. In the next section, we will look at how to work with environment variables in Heroku.

Why are Environment Variables important in Heroku?

Environment variables are important in Heroku because they enable developers to store configuration information, such as API keys, database credentials, and other sensitive data, outside of their source code. This not only keeps the codebase clean but also enhances security by preventing accidental exposure of such information. In Heroku, environment variables can be set for an entire app or specific to individual dynos, and they can be easily updated without having to modify the code directly. This flexibility allows for greater scalability and ease of management, particularly in complex systems with many components. Additionally, using environment variables in Heroku makes it easier to maintain consistency between development and production environments, since variables can be set differently based on the environment. Overall, incorporating environment variables into the deployment process offers a more secure and efficient way to manage sensitive information in Heroku apps.

How to add Environment Variables in Heroku:

To add Environment Variables in Heroku, you'll first want to navigate to your app dashboard and select the Settings tab. Under the Config Vars section, you can add key-value pairs for your environment variables. You can also manage your environment variables programmatically using the Heroku CLI.

One simple way to add environment variables is to use the os library in Python. You can import the os library and use the os.environ object to access and modify environment variables. Below is an example code snippet that sets the value of an environment variable named MY_VAR to "hello world":

import os

os.environ['MY_VAR'] = 'hello world'

In this code, we first import the os library. Then we use the os.environ object to set the value of the MY_VAR environment variable to "hello world".

Another way to add environment variables is to use the Python-dotenv library. This library allows you to define your environment variables in a .env file and load them into your Python script using the dotenv.load_dotenv() method. This can be especially useful if you want to keep your environment variables separate from your codebase.

To use Python-dotenv in your Heroku app, you'll need to install it using pip and configure a Procfile to load it. Below is an example Procfile that loads the .env file and runs a Python script named app.py:

web: python -m dotenv -f .env run app.py

In this Procfile, we use the -m option to load the Python-dotenv module and the -f option to specify the path to the .env file. Then we run the app.py script as usual.

By using these simple code examples, you can quickly and easily add environment variables in Heroku and unlock the power and flexibility of your application.

Method 1: Using the Heroku Dashboard

One of the easiest ways to add environment variables on Heroku is through their dashboard. First, log in to your account and navigate to the specific app you want to modify. Click on the "Settings" tab and scroll down to the "Config Vars" section. Here, you can add and edit existing variables by clicking on the "Reveal Config Vars" button.

To add a new environment variable, simply click on the "Add" button and enter the key-value pair. You can add as many variables as you need for your application to function properly, depending on the requirements of your code. It is important to note that the keys are case-sensitive, so be consistent with the format throughout your code.

Once you have added all the necessary variables, be sure to save your changes by clicking on the "Save" button at the bottom of the page. The new variables should become available to your application immediately.

Using the Heroku Dashboard to manage environment variables is a simple and straightforward method, especially for those who are new to the platform. However, it may not be the most efficient method for larger applications or those with more complex variable requirements. In those cases, it may be beneficial to use command-line tools or third-party add-ons to streamline the process.

Method 2: Using the Heroku CLI

Another way to add environment variables to your Heroku app is by using the Heroku CLI. This method allows you to easily manage your app's configuration variables by typing commands in your terminal.

To get started, open your terminal and log in to your Heroku account by typing:

$ heroku login

Then, navigate to the root directory of your app and set the environment variable using the following command:

$ heroku config:set KEY=VALUE

Replace KEY and VALUE with your actual environment variable and its value. You can add as many environment variables as you need by running the above command multiple times.

To confirm that your environment variable has been successfully added, you can run the following command:

$ heroku config

This will display a list of all the environment variables currently set for your app.

Using the Heroku CLI to manage your app's environment variables can be a quick and efficient way to configure your app. However, it's important to ensure that you're logged in to the correct account and to only give access to those who need it. As always, ensure that you're following best practices when it comes to app security.

Method 3: Adding Environment Variables programmatically

If you're comfortable with Python code, you might prefer to add your environment variables programmatically. This is a great option if you're managing complex Heroku applications or if you prefer to keep your deployment process automated.

To get started with this method, open your preferred text editor and create a new Python file. You can name it anything you want, as long as it ends in .py.

Next, you need to import the os module, which allows you to interact with the operating system. To do this, add the following line at the top of your Python file:

import os

Now you're ready to start adding your Heroku environment variables. Here's an example of how to do this programmatically:

os.environ['MY_VARIABLE'] = 'my_value'

Replace MY_VARIABLE with the name of your environment variable and my_value with the value you want to assign to it. You can add as many environment variables as you need using this method.

Once you've added all of your environment variables, save your Python file and deploy it to Heroku. You should be able to access your environment variables from within your Heroku application using the os.environ.get() method.

Remember, the key to mastering programming is practice. So experiment with different methods of managing Heroku environment variables and see what works best for you!

Example 1: Adding Environment Variables in a Node.js app

Adding environment variables in your Node.js app running on Heroku is easy. First, open your terminal and navigate to your project directory. Then, create a .env file in the root directory of your project by typing touch .env in the terminal.

Next, add the environment variables you want to use in your app in the format VAR_NAME=value. For example, you might add:


Save your changes and add the .env file to your .gitignore file so that the file is not accidentally committed to your repository.

Now, you can access these environment variables in your Node.js app using the process.env object. For example, you might use:

const apiKey = process.env.MY_SECRET_API_KEY;
const port = process.env.PORT || 3000; // fallback to 3000 if not specified

That's it! By adding environment variables to your Node.js project, you can easily change configuration settings without having to modify your code or deploy a new version of your app.

Example 2: Adding Environment Variables in a Python app

If you are working with a Python app on Heroku, you will need to add environment variables to your app in order to store sensitive data, such as passwords and API keys. Here's how you can do it in a few easy steps:

  1. Open your terminal and navigate to the root directory of your app.

  2. Run the following command to add the environment variable:

$ heroku config:set KEY=value

Replace KEY with the name of the variable and value with the value that you want to set. For example, if you want to set a variable named "SECRET_KEY" with a value of "mysecretkey", you would run the following command:

$ heroku config:set SECRET_KEY=mysecretkey
  1. In your Python code, you can access the environment variable using the following code:
import os

SECRET_KEY = os.environ.get('SECRET_KEY')

This code will retrieve the value of the SECRET_KEY environment variable and store it in the SECRET_KEY variable in your Python code.

By adding environment variables to your Python app on Heroku, you can ensure that your sensitive data is secure and protected from unauthorized access. Make sure to follow best practices for managing your environment variables, such as avoiding hard-coded values in your code and rotating your keys regularly. Happy coding!

Example 3: Adding Environment Variables in a Ruby app

To add environment variables in a Ruby app running on Heroku, follow these simple steps. First, open your project directory and create a new file called .env. This file will contain all your environment variable declarations.

Next, add your environment variables to the .env file using the following syntax:


For example, if you want to declare a variable called DATABASE_URL with a value of localhost:5432, you'd do it like this:


Once you've added all your environment variables to the .env file, you need to load them into your Ruby app. The easiest way to do this is by using the dotenv gem.

To install the dotenv gem, add this line to your Gemfile:

gem 'dotenv', '~> 2.7'

Then run bundle install to install the gem.

Finally, load the environment variables into your app by adding the following line to config/application.rb:



And that's it! Your Ruby app is now ready to use environment variables. Remember to keep your .env file secret and never commit it to a public repository.

Conclusion and Further Reading

Congratulations, you've learned how to add environment variables to your Heroku app! This is a powerful tool that can help you keep your sensitive information secure, while still allowing you to use it in your code. Remember to always keep your secret keys as secret as possible, and to add them to your Heroku app as environment variables whenever you can.

If you're interested in learning more about Heroku, environment variables, or Python in general, there are plenty of resources out there to help you. Some great places to start include:

  • The Heroku Dev Center: This is the official documentation for Heroku, and it includes lots of helpful articles and tutorials on all aspects of the platform.
  • The Python documentation: Likewise, the official Python documentation is a fantastic resource for learning the language itself.
  • Stack Overflow: This is a popular Q&A site for developers, and it's a great place to go if you have specific questions about using Heroku, environment variables, or Python.
  • Twitter: Finally, following some Python developers and companies on Twitter can be a great way to stay up-to-date on the latest news and trends in the community.

Remember, the most important thing when learning Python is to keep practicing and experimenting. Don't be afraid to try new things, make mistakes, and learn from them. That's the only way you'll truly unlock the power of Heroku, and Python as a whole. Good luck!

As an experienced software engineer, I have a strong background in the financial services industry. Throughout my career, I have honed my skills in a variety of areas, including public speaking, HTML, JavaScript, leadership, and React.js. My passion for software engineering stems from a desire to create innovative solutions that make a positive impact on the world. I hold a Bachelor of Technology in IT from Sri Ramakrishna Engineering College, which has provided me with a solid foundation in software engineering principles and practices. I am constantly seeking to expand my knowledge and stay up-to-date with the latest technologies in the field. In addition to my technical skills, I am a skilled public speaker and have a talent for presenting complex ideas in a clear and engaging manner. I believe that effective communication is essential to successful software engineering, and I strive to maintain open lines of communication with my team and clients.
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