Method for downloading YouTube video thumbnails

youtube-thumbnail-download.py

import requests
from typing import Optional

def download_youtube_thumbnail(video_id: str, filename: Optional[str] = 'image.jpg') -> None:
    """
    Method for downloading youtube thumbnail (if explicitly set by the
    publisher) in maximum resolution. If filename is not passed then the
    image will be saved as 'image.jpg'.
    
    Args:
        video_id:   str:    Unique ID of the video for which the thumbnail is to be downloaded.
                            e.g., https://www.youtube.com/watch?v=12345678910, in this link
                            '12345678910' is the video_id (length 11)
        filename:   str:    File of the image to be saved. (Default is 'image.jpg')
    Returns:
        None
    """
    url = 'https://img.youtube.com/vi/{}/maxresdefault.jpg'.format(video_id)
    with open(filename, 'wb') as file:
        file.write(requests.get(url).content)
    print('Image saved as {}!'.format(filename))
    return