n-dim permutation matrix/generator?
Anton Vredegoor
anton.vredegoor at gmail.com
Mon Nov 20 15:26:33 CET 2006
robert wrote:
> for the purpose of flat n-dim iteration a function or generator
> ndim_permute(*v) should compute or generate a list of tuples like:
>
> ndim_permute( (0,1,2), (0,1), (0,1), ) ->
>
> 0 0 0
> 0 0 1
> 0 0 2
> 0 1 0
> 0 1 1
> 0 1 1
hmm ... shouldn't his be (0 1 2) ?
> 1 0 1
> ....
>
>
> what is a good solution? Or is there already a total iterator existing
> somewhere in the stdlib?
I think there are good solutions in the python cookbook at:
http://aspn.activestate.com/ASPN/Cookbook/Python
But it gives a page mentioning 'system difficulties' now, so I can't
check. Someone else will post the link to their favorite recipe.
Meanwhile, this gives me a chance to plug some of my experimental code :-)
A.
def ncycle(seq,n):
while True:
for x in seq:
for dummy in xrange(n):
yield x
def cross(*args):
p,R = 1,[]
for arg in args:
L = list(arg)
R.append(ncycle(L,p))
p *= len(L)
R.reverse()
for dummy in xrange(p):
yield tuple(x.next() for x in R)
def test():
for x in cross((0,1,2), (0,1), (0,1)):
print x
if __name__=='__main__':
test()
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