Viewing a nested list as a tree

The problem, as discussed in the last post, is to "flatten" a list of nested lists of unspecified structure. One can look at such an object as a tree.

I thought about writing code to do a "depth-first traversal" of this tree, but then I remembered PyCogent. It has functions that manipulate trees. All we have to do is to convert our data to a form that it can recognize:

>>> L = [[[1, 2, 3], [4, 5]], 6] >>> `L` '[[[1, 2, 3], [4, 5]], 6]' >>> t = `L`.replace('[','(') >>> t = t.replace(']',')') + ';' >>> t '(((1, 2, 3), (4, 5)), 6);'

It's easiest to load the data from a file, so first we write it:

>>> FH = open('temp.tree','w') >>> FH.write(t) >>> FH.close() >>> >>> from cogent import LoadTree >>> tr = LoadTree('temp.tree') >>> tr Tree("(((1,2,3),(4,5)),6);") >>> >>> print tr.asciiArt() /-1 | /edge.0--|--2 | | /edge.2--| \-3 | | | | /-4 -root----| \edge.1--| | \-5 | \-6 >>> >>> [str(tip) for tip in tr.iterTips()] ['1;', '2;', '3;', '4;', '5;', '6;']