Build an M3U Playlist from Folder MP3s in Python

from pathlib import Path
import sys


def build_playlist(folder: str, output: str = "playlist.m3u") -> str:
    folder_path = Path(folder)
    if not folder_path.is_dir():
        raise FileNotFoundError(f"Folder not found: {folder}")

    mp3_files = sorted(folder_path.glob("*.mp3"))
    if not mp3_files:
        print("No MP3 files found in the folder.")
        return ""

    lines = ["#EXTM3U"]
    for mp3 in mp3_files:
        lines.append(f"#EXTINF:-1,{mp3.stem}")
        lines.append(mp3.resolve().as_uri())

    playlist_path = folder_path / output
    playlist_path.write_text("\n".join(lines) + "\n", encoding="utf-8")
    return str(playlist_path)


if __name__ == "__main__":
    if len(sys.argv) > 1:
        folder_input = sys.argv[1]
    else:
        folder_input = "."

    result = build_playlist(folder_input)
    if result:
        print(f"Playlist created: {result}")