great thanks to all.
actually i have not seen it was a cross product... :) but then there
are already few others ideas from the web, i paste what i have found
below...
BTW i was unable to choose the best one, speaking about performance
which one should be prefered ?
### --------------------------------------------------
### from title: variable X procuct - [(x,y) for x in list1 for y in
list2]
### by author: steindl fritz
### 28 mai 2002
### reply by: Jeff Epler
def cross(l=None, *args):
if l is None:
# The product of no lists is 1 element long,
# it contains an empty list
yield []
return
# Otherwise, the product is made up of each
# element in the first list concatenated with each of the
# products of the remaining items of the list
for i in l:
for j in cross(*args):
yield [i] + j
### reply by: Raymond Hettinger
def CartesianProduct(*args):
ans = [()]
for arg in args:
ans = [ list(x)+[y] for x in ans for y in arg]
return ans
"""
print CartesianProduct([1,2], list('abc'), 'do re mi'.split())
"""
### from:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/159975
### by: Raymond Hettinger
def cross(*args):
ans = [[]]
for arg in args:
ans = [x+[y] for x in ans for y in arg]
return ans
### from:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/159975
### by: Steven Taschuk
"""
Iterator version, Steven Taschuk, 2003/05/24
"""
def cross(*sets):
wheels = map(iter, sets) # wheels like in an odometer
digits = [it.next() for it in wheels]
while True:
yield digits[:]
for i in range(len(digits)-1, -1, -1):
try:
digits[i] = wheels[i].next()
break
except StopIteration:
wheels[i] = iter(sets[i])
digits[i] = wheels[i].next()
else:
break
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