Use C, C++ or Fortran for the heavy lifting, and Python for UI/business logic/non-high perf stuff for rapid app development.
It gets the job done, but the existence of Cython, Numba, Pythran, PyPy and many, many, others are indication that this isn't a global optimum.
Use C, C++ or Fortran for the heavy lifting, and Python for UI/business logic/non-high perf stuff for rapid app development.