Dotenv

Python · Reference cheat sheet

📋 Overview

python-dotenv loads a .env file into os.environ so local secrets stay out of source. Install: pip install python-dotenv. Call load_dotenv() early (app entrypoint), then read with os.getenv.

🔧 Core concepts

Typical .env lines: KEY=value (no quotes needed for simple values). Never commit real secrets — keep .env in .gitignore.

💡 Examples

Basic load:

import os
from dotenv import load_dotenv

load_dotenv()  # reads .env
db_url = os.getenv("DATABASE_URL")
debug = os.getenv("DEBUG", "0") == "1"
print(bool(db_url), debug)

Explicit path:

from pathlib import Path
from dotenv import load_dotenv
import os

env_path = Path(__file__).resolve().parent / ".env"
load_dotenv(env_path)
print(os.environ.get("API_KEY", ""))

Override existing vars:

from dotenv import load_dotenv
import os

os.environ["APP_ENV"] = "prod"
load_dotenv(override=True)  # .env wins
print(os.getenv("APP_ENV"))

Fail fast if required:

import os
from dotenv import load_dotenv

load_dotenv()
token = os.getenv("SECRET_TOKEN")
if not token:
    raise SystemExit("SECRET_TOKEN is required")

⚠️ Pitfalls

• load_dotenv does not raise if .env is missing — check return value or required keys.
• Default override=False: shell/CI env wins over .env.
• Values are strings; parse bools carefully ("false" is truthy in Python).
• Don’t commit .env; ship .env.example with dummy keys.
• Calling load_dotenv late (after code already read env) is a common bug.

🔗 Related

• Os
• Venv
• Pip
• Argparse