Skip to main content

Documentation Index

Fetch the complete documentation index at: https://python.datalumina.com/llms.txt

Use this file to discover all available pages before exploring further.

​
What is a .env file?

A .env file is a simple text file that stores your environment variables. Instead of typing export commands, you write them once in a file.

​
Basic setup

​
1. Install python-dotenv

pip install python-dotenv

​
2. Create .env file

Create a file named .env in your project: 
# .env
API_KEY=sk-1234567890abcdef
DATABASE_URL=sqlite:///myapp.db
DEBUG=True

​
3. Load in Python

from dotenv import load_dotenv
import os

# Load the .env file
load_dotenv()

# Now use your variables
api_key = os.environ.get('API_KEY')
debug = os.environ.get('DEBUG')

print(f"API Key: {api_key}")
print(f"Debug mode: {debug}")
That’s it! Much easier than export commands.

​
Critical: Add to .gitignore

Never commit .env files! They contain secrets. Add to .gitignore immediately:
# .gitignore
.env
.venv/
__pycache__/

​
Complete example

Here’s a real example with an API: 
# app.py
from dotenv import load_dotenv
import os
import requests

# Load environment variables
load_dotenv()

# Get API key
API_KEY = os.environ.get('OPENAI_API_KEY')

if not API_KEY:
    print("Please set OPENAI_API_KEY in .env file")
    exit(1)

# Use the API
headers = {"Authorization": f"Bearer {API_KEY}"}
# Make your API calls...
Your .env file: 
# .env
OPENAI_API_KEY=sk-your-actual-key-here
MODEL=gpt-3.5-turbo
MAX_TOKENS=100

​
Show others what they need

Create .env.example (this one you DO commit): 
# .env.example
OPENAI_API_KEY=your-api-key-here
MODEL=gpt-3.5-turbo
MAX_TOKENS=100
This shows other developers what variables they need without exposing your actual keys.

​
Rules for .env files

  • One variable per line
  • No spaces around =
  • No quotes (unless part of the value)
  • Use # for comments
  • Always UPPERCASE names

​
Common patterns

# API Keys
OPENAI_API_KEY=sk-...
GITHUB_TOKEN=ghp_...

# Database
DATABASE_URL=sqlite:///local.db

# Settings
DEBUG=True
PORT=8000
LOG_LEVEL=INFO

​
Quick tips

  1. Load early: Put load_dotenv() at the start of your program
  2. Use defaults: os.environ.get('PORT', '8000')
  3. Check your .gitignore: Make sure .env is listed
  4. Keep it simple: Only put configuration that changes

​
What’s next?

You now know how to manage secrets safely! Ready for modern Python tooling?

Modern Python

Next-level Python development