1) The Python version has some basic newbie coding errors. This sort of code is what Python programmers call "Java written in Python". It may be a valid algorithm in Java, but it's the wrong way to do it in Python. Code like this will work, but it will be slow. Depending on the size of "queries", you are potentially allocating gobs of memory in two different places for no reason, and then throwing it away without using it. I wouldn't be surprised if the examples in other languages had similar problems.
2) The JSON serializer in Django 1.4 uses a method which is known to be very slow, but which is easily portable across different platforms and works with older versions of Python. They no doubt included for easy bundling. In a real application you would probably want to simply use the normal JSON serializer from the standard library (which is many times faster).
3) The examples are little more than "hello world". I did some benchmark tests with several Python async frameworks, Pypy, and Node.js for an application I was working on. With small JSON objects there wasn't much difference in performance. Once you started using large JSON objects the performance lines for all versions were indistinguishable from each other. The performance bottlenecks were in libraries, and those standard libraries were all written in 'C', so interpreter versus compiler versus JIT made little difference.
4) The problem with "toy" examples is that in real life there are two performance factors which must be taken into account. Think of as y = mx + b. With a toy example you are probably only measuring "b". With most real life applications it's "m" that matters. There are often different optimization approaches that are best for varying ratios of "b" and "m". You have to know your application intimately and benchmark using data which is realistic for that application.
Python has a reputation for being "easy to learn". However, it is "easy" in the sense of being able to hack something together that works without knowing very much. There can be several different ways of doing things and doing it one way versus another way can mean a difference in performance of several orders of magnitude. The same may be true for some of the other languages, but I haven't examined them in enough detail to say.
2) The JSON serializer in Django 1.4 uses a method which is known to be very slow, but which is easily portable across different platforms and works with older versions of Python. They no doubt included for easy bundling. In a real application you would probably want to simply use the normal JSON serializer from the standard library (which is many times faster).
3) The examples are little more than "hello world". I did some benchmark tests with several Python async frameworks, Pypy, and Node.js for an application I was working on. With small JSON objects there wasn't much difference in performance. Once you started using large JSON objects the performance lines for all versions were indistinguishable from each other. The performance bottlenecks were in libraries, and those standard libraries were all written in 'C', so interpreter versus compiler versus JIT made little difference.
4) The problem with "toy" examples is that in real life there are two performance factors which must be taken into account. Think of as y = mx + b. With a toy example you are probably only measuring "b". With most real life applications it's "m" that matters. There are often different optimization approaches that are best for varying ratios of "b" and "m". You have to know your application intimately and benchmark using data which is realistic for that application.
Python has a reputation for being "easy to learn". However, it is "easy" in the sense of being able to hack something together that works without knowing very much. There can be several different ways of doing things and doing it one way versus another way can mean a difference in performance of several orders of magnitude. The same may be true for some of the other languages, but I haven't examined them in enough detail to say.