How to Build an argparse Command-Line Tool in Python

import argparse
import os
from pathlib import Path


def process_file(filepath, verbose=False):
    """Read a file and report its size and line count."""
    path = Path(filepath)
    if not path.exists():
        raise FileNotFoundError(f"File not found: {filepath}")

    content = path.read_text()
    lines = content.splitlines()
    size_kb = path.stat().st_size / 1024

    if verbose:
        print(f"Processing: {path}")
        print(f"Lines: {len(lines)}")
        print(f"Size: {size_kb:.2f} KB")
    else:
        print(f"{path}: {len(lines)} lines, {size_kb:.2f} KB")


def main():
    parser = argparse.ArgumentParser(
        description="Simple file info utility - counts lines and size"
    )
    parser.add_argument("filepath", type=str, help="Path to the file to analyze")
    parser.add_argument(
        "-v", "--verbose", action="store_true", help="Show extended processing details"
    )
    parser.add_argument(
        "-o", "--output", type=str, default=None, help="Write result to a file (optional)"
    )

    args = parser.parse_args()

    try:
        if args.output:
            with open(args.output, "w") as f:
                f.write(process_file(args.filepath, verbose=args.verbose))
        else:
            process_file(args.filepath, verbose=args.verbose)
    except FileNotFoundError as e:
        print(f"Error: {e}")
        return 1
    return 0


if __name__ == "__main__":
    exit(main())