paramspecli 0.3.0

Type-safe facade for the venerable argparse

paramspecli

paramspecli is a facade for the venerable argparse. It's simple, composable, and fun. But, most important, it's type-safe thanks to the ParamSpec magic.

Quick start

from paramspecli import Command, argument, option, flag


def ping(addr: str, *, until_stopped: bool, count: int | None):
    print(f"Pinging {addr} ...")


cli = Command(ping, prog="ping")
cli.bind(
    -argument("IP"),
    until_stopped=-flag("-t"),
    count=-option("-n", type=int),
)

result = cli.parse()
result()

Running it:

$ python ping.py -t -n 10 127.0.0.1
Pinging 127.0.0.1 ...

Type checker catches common errors:

cli.bind(
    # "bool" is not assignable to "str"
    -argument("IP", type=bool),
    # Type "bool | None" is not assignable to type "bool"
    until_stopped=-flag("-t", default=None),
    #
    # Argument missing for parameter "count"
)

IDE suggestions work too:

cli.bind(⏎
    (addr: str, *, until_stopped: bool, count: int | None) -> None

Installation

pip install paramspecli

Key points

paramspecli builds hierarchical CLIs with groups and commands.

• Commands match handler functions parameters with arguments and options.
• Arguments are bound to the handler's positional parameters.
• Options are bound to the handler's keyword parameters.
• Groups organize the commands. Groups may be nested. They could act like an intermediate commands, i.e. have own handlers, options and arguments.
• CLI 'compiles' to the argparse, runs it, then outputs the parse result.
• Parse result is a callable. Calling it invokes handlers along the route.

paramspecli supports several advanced argparse features: help sections, mutually exclusive options, options with the same destination. And adds a few own, like const options and passing contexts. It also includes a markdown documentation generator.

Read the documentation