[mikorym]

There was a post about Sage not long ago that it is used commonly among cryptographers.

As an aside, the statistical libraries and conveniences of R ("missing value" is a data type; every object is an array meaning you can call functions on arbitrary arrays) are the only reason that I still use R for some niche applications. I wonder whether pandas or something like Sage will actually take over this functionality. My impression is that the packages in R are so isolated (in a somewhat good sense) for a niche application that they are both difficult to emulate in Python and happen to keep on working long after they were written (and not necessarily maintained).