argparse-type-helper 0.2.4

an easy-to-integrate typed argument parser

Argparse Type Helper

A lightweight helper that lets you leverage type hints with argparse.

Installation

pip install argparse-type-helper

Features

• Class-based schema Bundle all your arguments in a single @targs-decorated class.
• Identical API Each field uses the same parameters as argparse.add_argument (help, action, nargs, etc.).
• Automatic registration One call to register_targs(parser, YourArgs) wires up all arguments on your ArgumentParser.
• Typed extraction After parse_args(), call extract_targs() to get a fully-typed instance of your class.
• Hybrid usage Mix native parser.add_argument(...) calls with class-based definitions in the same parser.
• Docstring support Use docstrings to automatically generate help text for your arguments.

Why not typed-argparse?

typed-argparse is a great library, but it replaces the familiar argparse.add_argument API with its own argument-definition interface, which can be a hurdle when integrating into an existing codebase.

argparse-type-helper, by contrast, is a simple helper that allows you to use type hints with argparse with minimal learning curve. It uses the same argparse API you’re already familiar with, and you can even mix native argparse usage with class-based definitions in the same parser.

Usage

import argparse
import sys
from typing import Never

from argparse_type_helper import (
    Flag,
    Name,
    extract_targs,
    post_init,
    register_targs,
    targ,
    targs,
)


# Define your typed arguments as a targ class
@targs
class MyArgs:
    # This example will show the common usage of targ.

    positional: str = targ(Name, help="A positional argument (positional).")
    custom_name_pos: str = targ(
        "my_positional", help="A custom named positional argument."
    )

    optional: str = targ(Flag, help="An optional argument (--optional).")
    optional_dash: str = targ(
        Flag, help="underscore is replaced with dash (--optional-dash)."
    )
    optional_short: str = targ(
        Flag("-s"), help="You can also add a short name (-s, --optional-short)."
    )
    custom_name_opt: str = targ(
        "--my-optional",
        help="A custom named optional argument.",
    )
    custom_name_opt_short: str = targ(
        ("-c", "--my-short-optional"),
        help="A custom named optional argument with a short name. (note the tuple)",
    )

    options: list[str] = targ(
        Flag,
        action="extend",
        nargs="+",
        default=[],
        help="All options (`help`, `action`, `nargs`, etc.) are the same as argparse.",
    )
    choices: str = targ(
        Flag,
        choices=["option1", "option2", "option3"],
        help="Another example argument with choices.",
    )
    flag: bool = targ(
        Flag("-d"), action="store_true", help="Another example boolean flag."
    )

    default_type: int = targ(
        Flag,
        default=42,
        help="if type is not specified, it defaults to the type hint. (type=int in this case)",
    )
    custom_type: float = targ(
        Flag,
        type=lambda x: round(float(x), 1),
        default=3.14,
        help="You can also specify a custom type",
    )

    docstring_as_help: str = targ(Flag, default="default value")
    """
    If you don't specify a help, it will use the docstring as the help text.
    This is useful for documentation purposes.
    Your LSP will also pick this up.
    """

    # You can also use the `post_init` decorator to execute some code after the arguments are extracted.
    # This is useful for validation or other post-processing.
    @post_init
    def validate(self) -> None:
        if self.positional == "error":
            raise ValueError("positional argument cannot be 'error'")


# You can register the targs with a custom parser
class MyParser(argparse.ArgumentParser):
    def error(self, message: str) -> Never:
        sys.stderr.write("error: %s\n" % message)
        self.print_help()
        sys.exit(2)


if __name__ == "__main__":
    # Create a parser
    parser = MyParser(description="Process some data arguments.")

    # Register the targs with the parser
    # verbose=True will print the registered arguments
    register_targs(parser, MyArgs, verbose=True)

    # Hybrid usage example
    parser.add_argument("--version", action="version", version="MyArgs 1.0.0")

    # Parse the arguments
    args = parser.parse_args()

    # Extract the targs from the parsed arguments
    my_args = extract_targs(args, MyArgs)
    print(f"Parsed arguments: {my_args}")