Examples

Below is a collection of standalone examples of specific argument/CLI behavior one might want, with comparison examples of how it might be done in each of Click/Typer/Argparse, where relevant.

Custom Option Value Name

i.e. “FOO” in

$ prog --help
Usage: prog --some-arg FOO

Cappa

from typing import Annotated
from dataclasses import dataclass
import cappa

@dataclass
class Args:
    some_arg: Annotated[str, cappa.Arg(value_name='FOO')]

cappa.parse(Args)

Argparse

import argparse

parser = argparse.ArgumentParser()
parser.add_argument("--some-arg", metavar="FOO")
parser.parse_args()

Click

import click

@click.command()
@click.option('--some-arg', metavar="FOO")
def main():
   ...

main()

Typer

from typing_extensions import Annotated
import typer

def main(some_arg: Annotated[str, typer.Argument(metavar="FOO")]):
   ...

typer.run(main)

Unbounded option arguments

i.e. prog --foo 1 2 3 4 ...

Cappa

from typing import Annotated
from dataclasses import dataclass
import cappa

@dataclass
class Args:
    foo: Annotated[list[str], cappa.Arg(num_args=-1)


print(cappa.parse(Args))

Argparse

import argparse

parser = argparse.ArgumentParser()
parser.add_argument("--foo", nargs="*")
print(parser.parse_args())

Click/Typer

Click’s (and thus Typer) parser, at time of writing, appears to not support this feature

Interactive Prompt

$ prog
What's your name?: Ron

Cappa

from typing import Annotated
from dataclasses import dataclass
from rich.prompt import Prompt
import cappa

@dataclass
class Args:
    some_arg: Annotated[str, cappa.Arg(default=rich.Prompt("What's your name?"))]

cappa.parse(Args)

Argparse

Argparse requires custom code or a third party library to support this feature

Click

import click

@click.command()
@click.option('--name', prompt="What's your name?")
def main(name):
    ...

main()

Typer

import typer
from typing_extensions import Annotated

def main(name: str, lastname: Annotated[str, typer.Option(prompt="What's your name?")]):
    ...

typer.run(main)