I mostly use Python for data analysis, statistical testing, and plotting. I learned this quite haphazardly. I began with a short online Python tutorial that took a few days to complete, and then I picked things up as I had new needs.
Before that, I used ROOT and Matlab. For ROOT, I learned a bit through the CERN ROOT tutorial, but mostly through working on LHC data and under the supervision of older graduate students. For Matlab, I learned it through a course in undergrad.
Finally, I use Unix shell scripting, which I learned through Zed Shaw's "Learn Command Line Interface the Hard Way." I liked it a lot! It can be found here: https://cglab.ca/~morin/teaching/1405/clcc/book/cli-crash-course.html
