If you're interested in this topic, you should watch this talk by Steven G. Johnson: https://www.youtube.com/watch?v=jhlVHoeB05A

tl;dr of the talk: Syntax has little to no effect on how a language performs. What distinguishes Julia from Python is that Julia's semantics were designed to be amenable to type inference. The results of type inference allow Julia's compiler to generate very efficient machine code.