permuting several lists (was Re: [Python-Dev] zip() and list-comprehension with commas)
Wed, 12 Jul 2000 09:52:42 +0200 (MEST)
Barry A. Warsaw:
> >>>>> "KY" == Ka-Ping Yee <email@example.com> writes:
> KY> I like this idea. This whole parallel iteration thing could
> KY> be solved with a single built-in and no syntax changes.
> KY> for x, y in parallel([10, 20, 30], [1, 2]):
> KY> Or "zip", since you're zipping the lists together (i foresee
> KY> potential geometric or concurrency-related interpretations of
> KY> "parallel"):
> Definitely +1 on concept. The nice bit is that parallel() or zip()
> can return objects that iterate efficiently. -0 on zip(), +0 on
> parallel(), +0 on making them builtins.
+1 on the concept.
-1 on calling it 'zip' (I was first thinking of Info ZIP and zlib).
-0 on calling it 'parallel' (makes me thinking of threads and processes).
What about calling this function 'permute()'?
Here is a strawman to play with:
"""takes several sequences as arguments and returns a list of tuples,
where each tuple contains an element of each sequence permutated
through all possible combinations."""
if len(args) == 1:
return map(lambda x:(x,), args)
res = ; cdr = apply(permute, args[1:])
for left in args:
for right in cdr:
res.append((left,) + right)
for x, y in permute([10, 20, 30], [1, 2]):
print "x, y =", x, y
BTW: How comes, that Ping very often invents or introduces very clever
ideas and concepts, but also very often chooses unclear names for them?
Is it just me not being a native english speaker?