On Sat, 11 Nov 2006 17:42:32 -0800, Dustan wrote: >> alright, let's try again: why do you need a self-contained reduce >> replacement that can be embedded inside a list comprehension ? >> >> </F> > > >>>> foo =\ > [[[1,2,3],[4,5,6],[7,8,9]], > [[3,2,1],[6,5,4],[9,8,7]]] > > Here, foo appears to be a 3-dimensional list - except it's supposed to > be 2-dimensional. The inner-list-of-lists is a result of how I'm > producing the data, and now I want to do a mass-concatenation (or > extending) of the inner-list-of-lists, and come up with this result: > >>>> foo == [[1,2,3,4,5,6,7,8,9],[3,2,1,6,5,4,9,8,7]] > True > > What's the best way to accomplish this?
I don't know if this is the best, but it didn't take long to come up with it: >>> foo = [[[1,2,3],[4,5,6],[7,8,9]], ... [[3,2,1],[6,5,4],[9,8,7]]] >>> >>> def unroll(list3d): ... newl = [] ... for sublist in list3d: ... newl.append(sum(sublist, [])) ... return newl ... >>> bar = unroll(foo) >>> bar [[1, 2, 3, 4, 5, 6, 7, 8, 9], [3, 2, 1, 6, 5, 4, 9, 8, 7]] Repeat after me: "Not everything has to be a one-liner." If sum() is too slow, because your sub-lists are huge, you can easily factor that out and replace it with something using extend. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
