python-dotenv

python-dotenv does one thing well: loading environment variables from .env files during development. The API is dead simple - `load_dotenv()` at app startup and you're done. It handles variable expansion, quotes, and multiline values intuitively. The `find_dotenv()` function walks up directories to locate your .env file, which is convenient for testing nested modules.

From a security perspective, it's mostly safe but requires discipline. The library itself doesn't validate or sanitize values - it's a dumb key-value loader. The real risk is developer behavior: .env files containing secrets often get committed to repos despite .gitignore. The library provides no warnings or safeguards here. Error handling is minimal but acceptable - missing files fail silently by default, which is usually what you want in production.

One gotcha: `override=True` will replace existing environment variables, which can cause confusion in containerized environments where you expect platform-injected secrets to take precedence. Always use the default `override=False` in production code paths.

I've used python-dotenv across dozens of projects and it just works. The core API is literally two lines: `from dotenv import load_dotenv; load_dotenv()` and you're done. It reads your .env file and makes everything available via `os.getenv()`. The learning curve is essentially zero - if you understand environment variables, you already know how to use this package.

Error handling is sensible and unobtrusive. Missing .env files fail silently by default (which is what you want in production), but you can use `load_dotenv(verbose=True)` or `dotenv_values()` when debugging. The package handles encoding issues gracefully, supports comments and multiline values, and respects existing environment variables by default (though you can override with `override=True`).

The documentation is straightforward with practical examples for common scenarios like using different .env files per environment or integrating with frameworks like Flask and Django. When things go wrong, it's usually user error (wrong file path, syntax issues in .env), and the package provides helpful utilities like `find_dotenv()` to locate your file automatically.

python-dotenv does exactly what it promises: loads .env files into environment variables with minimal fuss. The `load_dotenv()` call is straightforward and the `find_dotenv()` helper makes it easy to locate files up the directory tree. Variable expansion and multiline value support work reliably, and the API is intuitive enough that you rarely need to check docs.

From a security perspective, this is a double-edged sword. The library itself has minimal attack surface—no network calls, no complex parsing vulnerabilities in recent versions. However, it encourages a pattern that's great for local development but dangerous in production if misused. I've seen teams accidentally commit .env files with secrets, or worse, deploy containers that bundle .env files with credentials baked in. The library doesn't validate or sanitize values, which is correct behavior, but means you need discipline around secret management.

Error handling is quiet by default—if the .env file is missing, `load_dotenv()` returns False without raising exceptions. This is usually what you want, but can mask configuration issues during deployment if you're not checking return values.