I am in class 12. what should I do to study more about python and get a better package value?

Dear Ajay, I feel very delighted to know you have a clear image in your mind what you have to do in future that's good. Python is now the most trending programming language because it offers lots of libraries which are not available in other languages. Dear, you can learn through online courses from Simplilearn,udacity and coursera. These platforms offer very good course till beginning to a higher level with the real-life project and provide a certificate which helps you in placements. Data science is the very fast growing field in the world and python play a major role in it.

Learn hard, practice more, you get good salary don't worry if you start learning after 12th.

Best of luck dear Ajay.