Using `.env` Files

API_KEY = "sk-1234567890abcdef"
DATABASE_URL = "sqlite:///myapp.db"
DEBUG = True

Environment
──────────────────────────────
API_KEY=sk-xxxxxxxx
DATABASE_URL=...
DEBUG=True
PORT=8000
──────────────────────────────

        ↓

Python Application

import os

api_key = os.environ.get("API_KEY")

export API_KEY="sk-123456"
export DEBUG=True

import os

print(os.environ.get("API_KEY"))
print(os.environ.get("DEBUG"))

printenv

env

echo $API_KEY

export API_KEY=...
export DATABASE_URL=...
export SECRET_KEY=...
export PORT=8000
export DEBUG=True

# .env

API_KEY=sk-1234567890abcdef
DATABASE_URL=sqlite:///myapp.db
DEBUG=True
PORT=8000

pip install python-dotenv

from dotenv import load_dotenv
import os

load_dotenv()

import os

api_key = os.environ.get("API_KEY")
database = os.environ.get("DATABASE_URL")
debug = os.environ.get("DEBUG")
port = os.environ.get("PORT")

print(api_key)
print(database)
print(debug)
print(port)

os.environ["PORT"]

port = os.environ.get("PORT")

port = os.environ.get("PORT", "8000")

project/
│
├── .env
├── .gitignore
├── app.py
└── requirements.txt

OPENAI_API_KEY=sk-your-key
MODEL=gpt-4.1
MAX_TOKENS=200

from dotenv import load_dotenv
import os

load_dotenv()

API_KEY = os.environ.get("OPENAI_API_KEY")
MODEL = os.environ.get("MODEL")
MAX_TOKENS = os.environ.get("MAX_TOKENS")

print(API_KEY)
print(MODEL)
print(MAX_TOKENS)

OPENAI_API_KEY=your-api-key
DATABASE_URL=sqlite:///database.db
DEBUG=True
PORT=8000

cp .env.example .env

DATABASE_URL
API_KEY
SECRET_KEY

PORT=8000
DEBUG=True

PORT=8000

PORT = 8000

# Database
DATABASE_URL=sqlite:///db.sqlite3

# API Keys
OPENAI_API_KEY=...
GITHUB_TOKEN=...

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

# Application Settings
DEBUG=True
PORT=8000

# Authentication
SECRET_KEY=super-secret-key

# Logging
LOG_LEVEL=INFO

Create .env
      │
      ▼
Install python-dotenv
      │
      ▼
Call load_dotenv()
      │
      ▼
Read variables using os.environ.get()
      │
      ▼
Use them in your application