Why this script

  • Lightweight and self-contained.
  • Uses yt-dlp (actively maintained fork of youtube-dl) to fetch best video + audio and merge to MP4.
  • Auto-installs yt-dlp if not present, so you can get started quickly.

Requirements

  • Python 3.8 or newer
  • pip available
  • Internet connection
  • (Optional) ffmpeg on PATH for merging (yt-dlp will usually bundle merging if available)

Quick install

Option A — let the script auto-install yt-dlp (default behavior):

python youtubevideodownloder.py

Option B — install manually before running:

pip install --upgrade yt-dlp

How to use

  1. Save the script as youtubevideodownloder.py.
  2. Run the script:
python youtubevideodownloder.py
  1. When prompted, paste the YouTube video URL and press Enter. The video will be saved into a downloads/ directory by default.

Script (ready to paste)

import os
import re
import sys
import subprocess
import yt_dlp


def install_yt_dlp():
    """
    Install or upgrade yt-dlp.
    """
    try:
        subprocess.check_call([sys.executable, '-m', 'pip', 'install', '--upgrade', 'yt-dlp'])
        print("yt-dlp installed/upgraded successfully.")
    except subprocess.CalledProcessError:
        print("Failed to install yt-dlp. Please install manually using:")
        print("pip install --upgrade yt-dlp")


def sanitize_filename(filename):
    """
    Sanitize filename to remove invalid characters and limit length.
    """
    filename = re.sub(r'[^\w\-_\. ]', '_', filename)
    return filename.strip()[:200]


def download_youtube_video(youtube_url, output_dir='downloads'):
    """
    Download a YouTube video in HD format.
    """
    os.makedirs(output_dir, exist_ok=True)
    try:
        ydl_opts = {
            'format': 'bestvideo+bestaudio/best',
            'merge_output_format': 'mp4',
            'outtmpl': os.path.join(output_dir, '%(title)s.%(ext)s'),
            'nooverwrites': True,
            'no_color': True,
        }
        with yt_dlp.YoutubeDL(ydl_opts) as ydl:
            ydl.download([youtube_url])
        print("Download completed successfully.")
    except Exception as e:
        print(f"An error occurred: {e}")


def main():
    # Install or upgrade yt-dlp
    install_yt_dlp()

    video_url = input("Enter the YouTube video URL: ")
    download_youtube_video(video_url)


if __name__ == "__main__":
    main()

Explanation of important parts

  • install_yt_dlp() uses the current Python interpreter to run pip install --upgrade yt-dlp so the script can run even on fresh systems.
  • sanitize_filename() replaces unsafe characters and truncates long names to avoid filesystem errors.
  • download_youtube_video() sets format to bestvideo+bestaudio/best — this asks yt-dlp to download the best separate video and audio streams (if available) and merge them; otherwise it falls back to the best single stream.
  • merge_output_format: 'mp4' tells yt-dlp to produce an MP4 file after merging.

Customization ideas

  • Add command-line flags with argparse to accept --url, --output, or --no-install.
  • Change the template outtmpl to include %(id)s or timestamps to avoid collisions.
  • Force a specific resolution, e.g. format: 'bestvideo[height<=720]+bestaudio/best' to limit downloads to 720p.

Troubleshooting

  • If automatic installation fails, run:
pip install --upgrade yt-dlp

  • If merging fails (errors mentioning ffmpeg), install ffmpeg and add it to PATH.

  • For verbose debugging, run:

yt-dlp -v <VIDEO_URL>

Legal & Ethical note

Only download videos you have permission to download. Respect copyright and YouTube’s Terms of Service.

Where the script saves files

By default the script creates a downloads/ directory next to the script and saves files as the video title (sanitized). You can change output_dir when calling download_youtube_video() or modify outtmpl in the ydl_opts dictionary.