Declare program arguments in a type-safe way.
This project builds on top of argparse by adding type-safety and allowing a more expressive argument parser definition.
from arcparse import arcparser, flag, positional
from pathlib import Path
@arcparser
class Args:
path: Path = positional()
recurse: bool = flag("-r")
item_limit: int = 100
output_path: Path | None
args = Args.parse()
print(f"Scanning {args.path}...")
...Help output of this parser
usage: program.py [-h] [-r] [--item-limit ITEM_LIMIT] [--output-path OUTPUT_PATH] path
positional arguments:
path
options:
-h, --help show this help message and exit
-r, --recurse
--item-limit ITEM_LIMIT
--output-path OUTPUT_PATH
For more examples see Examples.
# Using pip
$ pip install arcparse- Positional, Option and Flag arguments
- Name overriding
- Multiple values per argument
- Type conversions
- Mutually exclusive groups
- Subparsers
- Parser inheritance (with overriding)
- Presence validation
This project was inspired by swansonk14/typed-argument-parser.
from __future__ import annotations makes all annotations strings at runtime. This library relies on class variable annotations's types being actual types. inspect.get_annotations(obj, eval_str=True) is used to evaluate string annotations to types in order to assign converters. If an argument is annotated with a non-builtin type which is defined outside of the argument-defining class body the type can't be found which results in NameErrors. This is avoidable either by only using custom types which have been defined in the argument-defining class body (which is restrictive), or alternatively by not using the annotations import which should not be necessary from python 3.14 forward thanks to PEP 649.