Comment by saamm

Thank you for this! I used it to make a little script to download audio from each lecture:

  youtube-dl --get-id https://www.youtube.com/playlist?list=PLyGKBDfnk-iAQx4Kw9JeVqspbg77sfAK0 -i > ids.txt
  while read id; do
      youtube-dl -f bestaudio https://www.youtube.com/watch?v=$id
  done < ids.txt