Python is plenty fast where it matters. You have heavily optimized numerical and scientific libraries (numpy and scipy) and can easily escape in C if it matters that much to you. But in my experience bad performance is usually a result of wrong architecture and algorithms, sometimes even outright bugs, often introduced by "optimization" hacks which only make code less readable.
This holds for all languages, of course, not only Python. Forget raw speed, it is just the other end of the stick from Hadoop. Believe me, you don't need it. And even when you think you do, you don't. And when you have measured it and you still need it, ok, you can optimize that bottleneck. Everywhere else, choose proper architecture and write maintainable code and your app will leave others in the dust. Because it is never just about the speed anyway.
I agree that it depends on what you're doing, and the speed of the language often doesn't matter -- that has to be the case or Python would never have caught on to begin with.
But you can write code in Common Lisp or Clojure that's just as readable and maintainable (once you learn the language, obviously) as anything you can write in Python, and the development experience is just as good if not better.
This holds for all languages, of course, not only Python. Forget raw speed, it is just the other end of the stick from Hadoop. Believe me, you don't need it. And even when you think you do, you don't. And when you have measured it and you still need it, ok, you can optimize that bottleneck. Everywhere else, choose proper architecture and write maintainable code and your app will leave others in the dust. Because it is never just about the speed anyway.