What you learn during your lifetime will
hopefully stay with you for the rest of your life. However, if you do not use the skills you have learned, they will get rusty, and if you do not sharpen them from time to time, you will find that they will be not any more readily usable in the moment when you will need them.
This was my state of mind when I discovered Cognitive.ai, a spin-off of IBM devoted to provide online courses about Big Data, Data Science, Machine Learning, Python, R, Scala etc.
Curiosity is a bestial instinct and pushed me to start taking courses from this platform (written using the OpenEdx framework, in a very clean and effective style) almost immediately.
And it provides a decent choice of courses too, especially for newbies. Courses are normally stand-alone but often organized in “Learning paths”, which are logically organized sequences of courses. Other platforms would call them “Specializations”.
They are not as deep in theory as other courses, but would form a basic curriculum for “application” of the tools and libraries they deal with. More than that, they would give the basic tools to get started to delve deeper in one or the other subjects. IBM is also offering the same type of courses on Coursera, in a version that is slightly augmented, containing additional chapters and courses, and with a Final Capstone at the end of the cycles.
Anyway the courses I have been following to date are all very easy for someone who has already taken a course with stronger theoretical foundations, like the Machine Learning by Andrew NG or the Data Science Specialization by Johns Hopkins on Coursera. The difference here is that the courses are made of, for the great part, of practice and the practice is done using Jupyter notebooks, which is a must tool to have in a Data Scientist’s toolbox. If you have it already? Well, there is always something you can learn, for instance a nuance in the use of a function of a function you did not know in a library or a parameter you did not explore. And I mean always.
Best of all this is that all courses are completely free of charge and all courses provide IBM badges and certificates after you pass the graded questions at the end of each module and the final exam.