There are several good answers already, but none of them so far deal with **high performance computing**, which nowadays means computing on tens or hundreds of thousands of cores. I am aware of only three Python codes that have scaled to this level: * [PyClaw][1] (my code -- you can read about it and my take on HPC software development in Python in [this paper][2]) * [GPAW][3] * [FiPy][4] Of course, you can't write a performant numerical code entirely in Python, so typically these use a compiled language for performance-critical parts (in PyClaw, we use both Fortran and C). One reason for choosing Python is that automated tools like f2py and Cython make it easy to incorporate compiled code. I do not believe there are any high performance computing codes written in the languages you mention. I suspect modern supercomputers don't support those languages. [1]: http://numerics.kaust.edu.sa/pyclaw/ [2]: http://arxiv.org/abs/1111.6583 [3]: https://wiki.fysik.dtu.dk/gpaw/ [4]: http://www.ctcms.nist.gov/fipy/