Generating all possible combination of elements in a list

[Mir Nazim]

Hello,

I need to write scripts in which I need to generate all posible unique
combinations of an integer list. Lists are a minimum 12 elements in
size with very large number of possible combination(12!)

I hacked a few lines of code and tried a few things from Python
CookBook (http://aspn.activestate.com/ASPN/Cookbook/), but they are
hell slow.

Does any body know of an algorithm/library/module for python that can
help me in generation of these combinations faster

"""ONLY REQUIREMENT IS SPEED"""

Example Problem:

Generate all possible permutations for
[1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2]

[1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2] (notice an extra 2 )

eliminate some combinations based on some conditions and combine the
rest of combinations. And now generate all possible combinations for
resulting data set.
Hope you get the idea.



Thanks 

PS: Tried matlab/scilab. They are slower than python.