Boolean CLI Options

We have seen some examples of CLI options with bool, and how Typer creates --something and --no-something automatically.

But we can customize those names.

Only --force

Let's say that we want a --force CLI option only, we want to discard --no-force.

We can do that by specifying the exact name we want:

Python 3.6+Python 3.6+ non-Annotated

import typer
from typing_extensions import Annotated


def main(force: Annotated[bool, typer.Option("--force")] = False):
    if force:
        print("Forcing operation")
    else:
        print("Not forcing")


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

Tip

Prefer to use the Annotated version if possible.

import typer


def main(force: bool = typer.Option(False, "--force")):
    if force:
        print("Forcing operation")
    else:
        print("Not forcing")


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

Now there's only a --force CLI option:

fast →💬 Check the helppython main.py --help
💬 Notice there's only --force, we no longer have --no-forceUsage: main.py [OPTIONS]

Options:
--force [default: False]
--help Show this message and exit.

💬 Try it:python main.py
Not forcing

💬 Now add --forcepython main.py --force
Forcing operation

💬 And --no-force no longer exists ⛔️python main.py --no-force
Usage: main.py [OPTIONS]
Try "main.py --help" for help.

Error: no such option: --no-force

restart ↻

Alternative names

Now let's imagine we have a CLI option --accept.

And we want to allow setting --accept or the contrary, but --no-accept looks ugly.

We might want to instead have --accept and --reject.

We can do that by passing a single str with the 2 names for the bool CLI option separated by /:

Python 3.6+Python 3.6+ non-Annotated

from typing import Optional

import typer
from typing_extensions import Annotated


def main(accept: Annotated[Optional[bool], typer.Option("--accept/--reject")] = None):
    if accept is None:
        print("I don't know what you want yet")
    elif accept:
        print("Accepting!")
    else:
        print("Rejecting!")


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

Tip

Prefer to use the Annotated version if possible.

from typing import Optional

import typer


def main(accept: Optional[bool] = typer.Option(None, "--accept/--reject")):
    if accept is None:
        print("I don't know what you want yet")
    elif accept:
        print("Accepting!")
    else:
        print("Rejecting!")


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

Check it:

fast →💬 Check the helppython main.py --help
💬 Notice the --accept / --rejectUsage: main.py [OPTIONS]

Options:
--accept / --reject
--help Show this message and exit.

💬 Try itpython main.py
I don't know what you want yet

💬 Now pass --acceptpython main.py --accept
Accepting!

💬 And --rejectpython main.py --reject
Rejecting!

restart ↻

Short names

The same way, you can declare short versions of the names for these CLI options.

For example, let's say we want -f for --force and -F for --no-force:

Python 3.6+Python 3.6+ non-Annotated

import typer
from typing_extensions import Annotated


def main(force: Annotated[bool, typer.Option("--force/--no-force", "-f/-F")] = False):
    if force:
        print("Forcing operation")
    else:
        print("Not forcing")


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

Tip

Prefer to use the Annotated version if possible.

import typer


def main(force: bool = typer.Option(False, "--force/--no-force", "-f/-F")):
    if force:
        print("Forcing operation")
    else:
        print("Not forcing")


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

Check it:

fast →💬 Check the helppython main.py --help
💬 Notice the -f, --force / -F, --no-forceUsage: main.py [OPTIONS]

Options:
-f, --force / -F, --no-force [default: False]
--help Show this message and exit.

💬 Try with the short name -fpython main.py -f
Forcing operation

💬 Try with the short name -Fpython main.py -F
Not forcing

restart ↻

Only names for False

If you want to (although it might not be a good idea), you can declare only CLI option names to set the False value.

To do that, use a space and a single / and pass the negative name after:

Python 3.6+Python 3.6+ non-Annotated

import typer
from typing_extensions import Annotated


def main(in_prod: Annotated[bool, typer.Option(" /--demo", " /-d")] = True):
    if in_prod:
        print("Running in production")
    else:
        print("Running demo")


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

Tip

Prefer to use the Annotated version if possible.

import typer


def main(in_prod: bool = typer.Option(True, " /--demo", " /-d")):
    if in_prod:
        print("Running in production")
    else:
        print("Running demo")


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

Tip

Have in mind that it's a string with a preceding space and then a /.

So, it's " /-S" not "/-S".

Check it:

fast →💬 Check the helppython main.py --help
💬 Notice the / -d, --demoUsage: main.py [OPTIONS]

Options:
/ -d, --demo [default: True]
--help Show this message and exit.

💬 Try itpython main.py
Running in production

💬 Now pass --demopython main.py --demo
Running demo

💬 And the short versionpython main.py -d
Running demo

restart ↻