Hi, guys. I'm racking my brain trying to figure out a generic way to do what the following Python code does for lists of three lists. I could just be stressed out and lacking sleep, but I don't see a good way!

[code]possibles = ['ABCDE', '12345', 'XYZ']

def compute_paths(lst):
paths = []

for a in lst[0]:
for b in lst[1]:
for c in lst[2]:
paths.append([a, b, c])

return paths

for path in compute_paths(possibles):
print ''.join(path)[/code]

This correctly outputs:
[code]A1X
A1Y
A1Z
A2X
A2Y
...
E4Y
E4Z
E5X
E5Y
E5Z[/code]

but I need to do it for any complexity. Thoughts?

How about this?  The level of indirection for the resulting list is a bit off, but that's a minor detail that you can fix if you care.

[code]
l = ['AB', '12', 'XZ']

def increment(i, c):
while c >= 0:
i[c] = i[c] + 1
if i[c] >= len(l[c]):
i[c], c = 0, c - 1
else:
break
return c

if len(l) <= 0:
sys.exit(0)
r = range(0, len(l))

p = []

i = [0 for c in r]
while True:
p.append([l[c][i[c]] for c in r])
if increment(i, c) < 0:
break
print p
[/code]

Sample output:
[code][['A', '1', 'X'], ['A', '1', 'Z'], ['A', '2', 'X'], ['A', '2', 'Z'], ['B', '1', 'X'], ['B', '1', 'Z'], ['B', '2', 'X'], ['B', '2', 'Z']][/code]

Not sure about any specific Python code, but you definitely want a recursive function--I think.

[quote author=Insolence link=topic=16744.msg169581#msg169581 date=1180584396]
Not sure about any specific Python code, but you definitely want a recursive function--I think.
[/quote]

Recursion, but Python has access to functional constructs that would make code a bit more elegant than procedural recursion.  :) 

But yes, recursion should be the way to go in this case, unless you're going to be nested on more than a couple orders of magnitude of complexity. ;)

[code]
possibles = ["ABCDE","12345","XYZ"]

def compute_paths(lst):
if len(lst) == 1:
return [[x] for x in lst[0]]
else:
r = []
for tail in compute_paths(lst[1:]):
for e in lst[0]:
r.append([e] + tail)
return r

for path in compute_paths(possibles):
print "".join(path)

[/code]

[quote author=Insolence link=topic=16744.msg169581#msg169581 date=1180584396]
Not sure about any specific Python code, but you definitely want a recursive function--I think.
[/quote]

You realize that's an oxymoron, right? :)

[quote author=Joe[x86] link=topic=16744.msg169606#msg169606 date=1180734812]
[quote author=Insolence link=topic=16744.msg169581#msg169581 date=1180584396]
Not sure about any specific Python code, but you definitely want a recursive function--I think.
[/quote]

You realize that's an oxymoron, right? :)
[/quote]

Python has some functional programming aspects, but it's not like say Haskell