Using environment variables when deploying Lambda containers

While building a simple application that pulls API location data for the International Space Station, I was running the ingestion and transformation script locally on my system, passing the necessary parameters to the CLI. Below is the code snippet of how I was going about this.

def main(params):
    user = params.u
    password = params.p
    host = params.host
    ...


if __name__ == "__main__":
    # Create the CLI parser
    parser = argparse.ArgumentParser(description="Call ISS API and store current position in Amazon RDS")

    # Create two CLI arguments to ask for username and password
    parser.add_argument("-u", help="username for Postgres")
    parser.add_argument("-p", help="password for Postgres")
    parser.add_argument("--host", help="hostname for RDS Postgres server")

    args = parser.parse_args()
    main()

Realising this wasn't probably going to work when deploying the container using a Lambda function, simply because Lambda does not support passing CLI arguments directly to the container. My research pointed me to a better implementation using environment variables to pass the -u, -p, and --host parameters to the container.

def main():
    # Read database credentials from environment variables
    user = os.getenv("POSTGRES_USER")
    password = os.getenv("POSTGRES_PASSWORD")
    host = os.getenv("POSTGRES_HOST")

    ...

    if __name__ == "__main__":
    main()

The result: a more elegant solution that works with a Lambda function calling the container stored in ECR.