Using python-dotenv in a Flask Application

python-dotenv is a package that allows you to manage environment variables in a .env file and load them into your Flask application. This is useful for handling sensitive information like database credentials, API keys, and other configuration settings without hardcoding them into your code.

1. Installing python-dotenv

First, install python-dotenv using pip:

pip install python-dotenv

2. Creating a .env File

Create a .env file in your project root directory and define environment variables:

FLASK_APP=app.py
FLASK_ENV=development
SECRET_KEY=mysecretkey
DATABASE_URL=mysql://user:password@localhost/dbname
DEBUG=True

3. Loading Environment Variables in Flask

In your app.py or config.py, use dotenv to load the environment variables:

import os
from dotenv import load_dotenv

# Load environment variables from .env file
load_dotenv()

# Flask Configuration
class Config:
    SECRET_KEY = os.getenv("SECRET_KEY", "default_secret")
    SQLALCHEMY_DATABASE_URI = os.getenv("DATABASE_URL")
    DEBUG = os.getenv("DEBUG", "False").lower() == "true"

Then, apply this configuration to your Flask app:

from flask import Flask
from config import Config

app = Flask(__name__)
app.config.from_object(Config)

4. Using Flask CLI with .env

Flask’s built-in CLI (flask run) automatically loads environment variables from a .env file if it contains FLASK_APP=app.py. Simply run:

flask run

This will start the Flask application with the configurations from .env.

1. Handling Different Data Types

Since os.getenv() reads values as strings, you may need to convert them:

class Config:
    DEBUG = os.getenv("DEBUG", "False").lower() == "true"
    PORT = int(os.getenv("PORT", 5000))

1. Using Flask-DotEnv (Alternative Method)

Another approach is to use Flask-DotEnv to automatically load .env:

pip install flask-dotenv

Modify app.py:

from flask import Flask
from flask_dotenv import DotEnv

app = Flask(__name__)
env = DotEnv()
env.init_app(app)  # Auto-load .env file

Conclusion

Using python-dotenv in a Flask application helps manage configurations securely and keeps sensitive information out of source code. By following this guide, you can easily integrate .env files into your Flask projects for better security and maintainability.