How fast can I learn Python for data science and its libraries?

See python programming is basically a user-friendly easy to learn language once you get basics on python, for data science especially there will be few libraries in python that you should need to get expertise in like pandas, numpy, matplotlib, sklearn etc. which helps you deploy your ideas and visualize data and that you can learn by getting into documentation and learning syntax, but the main concept is you should get to know what happens behind those functions learn the concept coding can be learnt easily.

There is no rocket science in learning python. Check this Python for Data Science Bootcamp before you start your journey into Data Science.