Setting options from environment variables when using argparse

Question

I have a script which has certain options that can either be passed on the command line, or from environment variables. The CLI should take precedence if both are present, a

Answer 1

Another option:

    parser = argparse.ArgumentParser()
    env = os.environ
    def add_argument(key, *args, **kwargs):
        if key in env:
            kwargs['default'] = env[key]
        parser.add_argument(*args, **kwargs)

    add_argument('--type', type=str)

Or this one, using os.getenv for setting default value:

parser = argparse.ArgumentParser()
parser.add_argument('--type', type=int, default=os.getenv('type',100))