[BangPypers] Tuples vs Lists, perfromance difference

[Anand Chitipothu]

> I didn't quite follow you here, I'm sorry.  I was chatting with someone in
> IRC a week back, and here's his theory. He says in languages such as Python
> or Perl, almost all I/O, database etc are all optimized in C and hence there
> should not be much of a difference when it comes to such programs.
>
> By that theory anything which's in Python that's written in C such as
> adding, multiplyiig should work as fast as C. However that's not the case
> as mentioned here
> http://wiki.python.org/moin/PythonSpeed/PerformanceTips#PythonisnotC

C libraries are fast, python interpreter is not. If you are doing most
of your work in a C library then your code will have comparable
performance with C code. Thats why libraries like PIL, numpy as pretty
fast.

When you are doing multiplication in a loop, there is overhead for
each python statement executed.

A simple python statement "x = y + z" translates to something like this:

    tmp1 = locals['y']
    tmp2 = locals['z']
    tmp3 = tmp1 + tmp2
    locals['x'] = tmp3

(this is pseudo code, not python)

It has to look up y and z in locals dictionary, do the addition and
put the result in locals dictionary back as x. The addition operation
might be as fast as C, but there is a overhead of 2 dictionary lookups
and one dictionary set.

Jython compiler can compile Python code into Java. It will be
worthwhile experience to experiment with it.

Anand