Thanks! My son was just debating what to do after Python, so I sent him this.
My son has programmed in Python and will be taking the intermediate Python AOPS class. I may get some books for him (and me -- I know Python too) on applications of Python in math. Several titles can be found searching "python math" on Amazon, and the book "Coding the Matrix: Linear Algebra through Applications to Computer Science" (2013) which uses Python and was used in an online course
https://www.coursera.org/course/matrix also looks interesting.
