Combinations or Permutations

[Chris Kaynor]

The itertools module (http://docs.python.org/library/itertools.html) has
both permutations and combinations functionality.

Chris


On Mon, Sep 20, 2010 at 1:54 PM, Seth Leija <fazzitron at gmail.com> wrote:

> I need to know how to generate a list of combinations/permutations
> (can't remember which it is). Say I have a list of variables:
>
> [a,b,c,d,...,x,y,z]
>
> I am curious if there is an optimized way to generate this:
>
> [[a,b],[a,c],[a,d],...,[x,z],[y,z]]
>
> I currently have an iteration that does this:
>
> #list.py
>
> from math import *
>
> list1=['a','b','c','d','e']
> list2=[]
> length=len(list1)
>
> for it1 in range(0 ,length):
>    for it2 in range(it1+1, length):
>        list2.append([list1[it1],list1[it2]])
>
> print list2
>
> However, this is one of the slowest parts of my function (beaten only
> by variable instantiation). I posted this on another forum looking to
> see if there was a different method completely. They said that my
> method was about as simple as it could get, but I might be able to
> find out how to optimize my code here.
>
> Thanks in advance.
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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