[DonaldPShimoda]

> Swift was designed for general purpose app development.

Swift is a general-purpose language, but I would say that its first purpose is for mobile development. (Or, at least, that's where it started.)

> Why would you use Swift as your new data science language when Julia was made for that purpose and Swift was not?

The author calls out Swift as being good because (1) TensorFlow is now supported for it specifically and (2) it is optimized for mobile development. The author seems to feel that being able to deploy machine learning applications to mobile devices (and optimized) is a great boon, and Python is not well-suited to this.