I like this reader comment
when you play with big quantities of data in science, the speed is
usually limited by inefficient code, not by inherent properties of
the language. When I crunch my 5 GB dataset, making a for loop a
little faster won't make my code run in a reasonable time -- but
moving to a sparse data representation or avoiding the loop
altogether will. Python makes those things easy, that's why it is a
game changer for science.