I mean, I'd say it depends on what you do. When I see grad students writing numeric simulations in python I do think that it would be more efficient to learn a language that is better suited for that. And I know I'll be triggering many people now, but there is a reason why C and Fortran are still here.

But if it is for something small, yeah of course, use whatever you like. I do most of my stuff in R and R is a lot of things, but not fast.