It looks like you need to copy your D array to a newly-allocated Numpy ndarray before you can pass it to Python. So there's no binary PyArrayObject interoperability between D & Python (right?). Copying large N-D arrays all the time sounds slow...
Also, I couldn't find any examples of invoking D functions from Python. In fact, I could only find mentions on the D mailing list of people reporting that they couldn't get it to work: http://forum.dlang.org/post/[email protected]...
By compiling (transpiling) to C, Nim really does have an unfair advantage in the interoperability challenge...
Yes, Julia is amazing! In the same time, if you want to write a package for Julia you _may_ need to use C/C++. D is going to have integration with Julia in 2016 ;)
Julia is really fast in 95% cases, but 5% still "make the weather". The pairwise summation is an example. I will post benchmarks D vs Julia next week ;)
I would say the biggest benefit of D is static typing. In Julia you can run a simulation and discover only after half an hour that you misspelled a function