CLI Arguments with Environment Variables

You can also configure a CLI argument to read a value from an environment variable if it is not provided in the command line as a CLI argument.

Tip

You can learn more about environment variables in the Environment Variables page.

To do that, use the envvar parameter for typer.Argument():

Python 3.7+Python 3.7+ non-Annotated

import typer
from typing_extensions import Annotated


def main(name: Annotated[str, typer.Argument(envvar="AWESOME_NAME")] = "World"):
    print(f"Hello Mr. {name}")


if __name__ == "__main__":
    typer.run(main)

Tip

Prefer to use the Annotated version if possible.

import typer


def main(name: str = typer.Argument("World", envvar="AWESOME_NAME")):
    print(f"Hello Mr. {name}")


if __name__ == "__main__":
    typer.run(main)

In this case, the CLI argument name will have a default value of "World", but will also read any value passed to the environment variable AWESOME_NAME if no value is provided in the command line:

fast →💬 Check the helppython main.py --help
Usage: main.py [OPTIONS] [NAME]

Arguments:
  [NAME]  [env var: AWESOME_NAME;default: World]

Options:
  --help                Show this message and exit.

💬 Call it without a CLI argumentpython main.py
Hello Mr. World

💬 Now pass a value for the CLI argumentpython main.py Czernobog
Hello Mr. Czernobog

💬 And now use the environment variableAWESOME_NAME=Wednesday python main.py
Hello Mr. Wednesday

💬 CLI arguments take precedence over env varsAWESOME_NAME=Wednesday python main.py Czernobog
Hello Mr. Czernobog

restart ↻

Multiple environment variables

You are not restricted to a single environment variable, you can declare a list of environment variables that could be used to get a value if it was not passed in the command line:

Python 3.7+Python 3.7+ non-Annotated

import typer
from typing_extensions import Annotated


def main(
    name: Annotated[str, typer.Argument(envvar=["AWESOME_NAME", "GOD_NAME"])] = "World",
):
    print(f"Hello Mr. {name}")


if __name__ == "__main__":
    typer.run(main)

Tip

Prefer to use the Annotated version if possible.

import typer


def main(name: str = typer.Argument("World", envvar=["AWESOME_NAME", "GOD_NAME"])):
    print(f"Hello Mr. {name}")


if __name__ == "__main__":
    typer.run(main)

Check it:

fast →💬 Check the helppython main.py --help
Usage: main.py [OPTIONS] [NAME]

Arguments:
  [NAME]  [env var: AWESOME_NAME, GOD_NAME;default: World]

Options:
  --help                Show this message and exit.

💬 Try the first env varAWESOME_NAME=Wednesday python main.py
Hello Mr. Wednesday

💬 Try the second env varGOD_NAME=Anubis python main.py
Hello Mr. Anubis

restart ↻

Hide an env var from the help text

By default, environment variables used will be shown in the help text, but you can disable them with show_envvar=False:

Python 3.7+Python 3.7+ non-Annotated

import typer
from typing_extensions import Annotated


def main(
    name: Annotated[
        str, typer.Argument(envvar="AWESOME_NAME", show_envvar=False)
    ] = "World",
):
    print(f"Hello Mr. {name}")


if __name__ == "__main__":
    typer.run(main)

Tip

Prefer to use the Annotated version if possible.

import typer


def main(name: str = typer.Argument("World", envvar="AWESOME_NAME", show_envvar=False)):
    print(f"Hello Mr. {name}")


if __name__ == "__main__":
    typer.run(main)

Check it:

fast →//Check the helppython main.py --help
💬 It won't show the env varUsage: main.py [OPTIONS] [NAME]

Arguments:
  [NAME]  [default: World]

Options:
  --help                Show this message and exit.

💬 But it will still be able to use itAWESOME_NAME=Wednesday python main.py
Hello Mr. Wednesday

restart ↻

Technical Details

In Click applications the env vars are hidden by default. 🙈

In Typer these env vars are shown by default. 👀