Unsorting(randomizing) a sequence

[Skip Montanaro]

    Ole> I've been writing an algorithm myself, but it's incredibly slow and
    Ole> I would like something quicker (of course :) )

Got this off the list a couple years ago.  Does the trick for me:

    def shuffle(lst):
	"randomize a list"
	for i in range(len(lst)-1,0,-1):
	    choice = int(whrandom.random() * i)
	    lst[choice], lst[i] = lst[i], lst[choice]

    >>> l = range(20)
    >>> shuffle(l)
    >>> l
    [4, 17, 12, 6, 7, 15, 1, 11, 16, 10, 5, 3, 9, 19, 0, 8, 18, 13, 14, 2]

Skip Montanaro	| http://www.mojam.com/
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