Parse Env Vars into Typed Dict in Python

import os
from typing import Any, Dict


def parse_env_vars(env_names: list[str], env: Dict[str, str] | None = None) -> Dict[str, Any]:
    """Parse a list of environment variable names into a typed dict.

    Each variable is parsed as:
    - bool: "true"/"false" (case-insensitive)
    - int: if it can be converted to an integer
    - float: if it can be converted to a float
    - str: fallback, original string value

    Missing variables default to None.
    """
    env = env or os.environ
    result: Dict[str, Any] = {}

    for name in env_names:
        raw_value = env.get(name)
        if raw_value is None:
            result[name] = None
            continue

        # Normalize the value for parsing
        value = raw_value.strip()
        lower = value.lower()

        if lower in ("true", "false"):
            result[name] = lower == "true"
        else:
            try:
                # Convert to int first (handles "10", "-5", "0x10")
                result[name] = int(value, 0)
            except ValueError:
                try:
                    # Then try float ("3.14", "-0.5", "1e4")
                    result[name] = float(value)
                except ValueError:
                    # Fall back to string
                    result[name] = value

    return result


if __name__ == "__main__":
    # Example usage with a mock environment
    mock_env = {
        "DEBUG": "true",
        "PORT": "8080",
        "TIMEOUT": "2.5",
        "APP_NAME": "my-service",
        "MISSING_VAR": None,
    }
    names = ["DEBUG", "PORT", "TIMEOUT", "APP_NAME", "MISSING_VAR"]
    parsed = parse_env_vars(names, mock_env)
    for key, value in parsed.items():
        print(f"{key}: {value!r} ({type(value).__name__})")