This script will help you to download all lecture videos of a specific course from NPTEL, it will download all your lectures very fast using multiple threadings.
pip install -r requirements.txt
Visit this link https://archive.nptel.ac.in/noc/noc_course.html, and grab any courses of any department, make sure it contains course_id like that 106106212/ in the end: https://archive.nptel.ac.in/courses/106106212/.
python3 downloader.py
Then, enter the course URL and press enter.