Interestingly most (if not all) python examples also work in julia. Instead of using sum one can also use count, which might be more readable:

julia> count(age > 17 for age in ages)

Or even shorter:

julia> count(ages .> 17)

Under the hood many of the functions are implemented using the reduce function (similar to / in APL):

julia> reduce(+,ages .> 17)

I think many languages in data science have been influenced by APL. But sometimes this influence come from an intermediate language like matlab.