Python hands down. Your concerns about speed are not actually relevant unless you are in the high performance computing world, in which case you can choose C or

Python hands down. Your concerns about speed are not actually relevant unless you are in the high performance computing world, in which case you can choose C or Fortran. For most any practical application, performance is not that important and library support dominates the calculus. Scikit-learn, scipy, et.al. are the nicest set of math/stat/ML libraries in existence today, you should be able to spend years learning about the things they do.