Converting function signature into CLI

concat_and_make_cli.py

import argparse
from pathlib import Path
import signature


def concat(folder: str, output: str = 'concat.txt', include_names: bool = True):
    """Concatenates a list of files from a folder and saves them into a single file."""
    p = Path(folder)
    files = []
    for filename in p.iterdir():
        content = filename.open('r').read().strip()
        if include_names:
            content = f'{filename}\n{content}\n'
        files.append(content)
    single = '\n'.join(files)
    Path(output).open('w').write(single)
    
    
def make_cli(func: callable):
    """Takes a Python function and builds ArgumentParser instance using the 
    function's signature.
    
    The function is called right after the parameters are parsed.
    """
    parser = argparse.ArgumentParser()
    sig = inspect.signature(func)
    empty = inspect._empty

    for param in sig.parameters.values():
        annot = param.annotation
        options = {}
        
        if annot is empty:
            ptype = str
        elif isinstance(annot, tuple):
            ptype, help_msg = annot
            if help_msg is not empty:
                options['help'] = help_msg
        else:
            ptype = annot
        options['type'] = ptype
        if param.default is empty:
            options['required'] = True
        else:
            options['default'] = param.default
            if annot is empty:
                options['type'] = type(options['default'])

        name = param.name.replace('_', '-')
        parser.add_argument(f'--{name}', **options)

    func(**vars(parser.parse_args()))
    
    
if __name__ == '__main__':
    make_cli(concat)