Python and STL efficiency

[bearophileHUGS at lycos.com]

Pebblestone:

>I heard that python's list is implemented as adjustable array.

Correct, an array geometrically adjustable on the right.


>Here's my lisp implementation:<

What's the memory size of a before computing b? You can compare it with
Python, that may need less memory (because the array contains
pointers).


>BTW, I couldn't install psyco on my system (ubuntu), gcc just prompt to me thousands of lines of errors and warnings.<

Find a Win box ;-)  It's already compiled for it (for Py 2.3, 2.4).


>Your python's example (use direct index array index) of my corresponding lisp code works slower than the version which use 'append'.<

For me (a slow PC) it's almost twice faster, computer life is usually
complex.
For me using the esplicit allocation + Psyco makes that program about 4
times faster (from 8 to 2 seconds).


>This let me think how python's list is implemented.<

You also have to think how the * allocation is implemented and many
other things :-)
The list implementation is rather readable, Python sources are online
too.


>Anyway, python's list is surprisingly efficient.<

But its access isn't that fast :-) Psyco helps.

Bye,
bearophile