Leveraging the .env file in Python

Whenever you’re programming, you may have some secret “codes”, such as your OpenAI key or Amazon AWS S3 bucket key.

When checking sensitive information into source control (such as Git), you do not want to include this in your code since it could get stolen.

So how do we circumvent this problem and “hide our key”?

There’s a few different ways we can do this, but in this post, we’ll be exploring the environmental variable file (or .env, for short).

What are environment variables?

Before diving into what this file is, I want to briefly hit on what an environment variable is.

Each time when you run a python script, a terminal is opened and the code is executed. Before the script runs, the terminal session can be configured with environment variables, which you can define in this file.

These variables can be updated or modified to influence the program’s execution environment.

Think of environment variables as a setting on your phone - it’s very similar to how you set your phone to silent mode or enable WiFi. Each setting on your phone dictates how it behaves in different situations.

What is an environment file (.env file)?

An .env file is simply a file that is used in projects to store configuration settings, environment variables, and sensitive information securely.

We want to avoid putting API keys in a Python script:

my_key = "mumbojumbo"

Instead, create a .env file and place your key into it and remember to source it (. /full/path/to/.env) to have the changes take effect. For example:

# Sample .env file
SECRET_KEY=your-secret-key-goes-here
DEBUG=True
API_KEY=your-api-key-goes-here
ANOTHER_API_SECRET=another-api-secret-goes-here

Reading the .env file with Python

To read this file using Python, you’ll need to have the python-dotenv package installed:

pip install python-dotenv

From here, you need to load it into your shell environment and use the os library to retrieve the variable:

import os
from dotenv import load_dotenv

load_dotenv() # loads .env into shell

my_key = os.environ.get('MY_KEY', None) # retrieve it

» Tidbit: the period in front of the file name states that it is a “hidden” file. Most file explorers will not show files that start with the period.

» Pro tip: use .get() when indexing the os.environ dictionary and set the default to None. This prevents a KeyError from happening.

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