Creating tree structured list from nested list

Question

I have a nested list:

l = [[1], [2,3], [2,4], [2,5], [2,5,6], [2,5,7], [2,5,8],[2,5,8,9], [10],[11,12]]

and I need the list to be in a tree structured nested list, for example:

l = [{1:[], 2:[3,4,{5: [6,7, {8: [9]}]}], 10: [], 11: [12]}]

I have gone through this post which generates a similar tree that I need, however that works with symmetric set of nested list. I have tried using groupby feature of the list item but could not generate a list in desired format. I suppose there is something in python to do it easily which I am currently missing. Some pointers will be appreciated.

@HYRY Item next in a list is a child of the item previous in the list. So in [2,5,6] 5 is a child of 2 and 6 is a child of 5. Basically I have to group the elements to form a tree like structure i.e. parent child relation. — Rahul
– Rahul, Commented Mar 16, 2013 at 12:12
Why the result is not like {1: {}, 2: {3: {}, 4: {}, 5: {8: {9: {}}, 6: {}, 7: {}}}, 11: {12: {}}, 10: {}} — Kabie
– Kabie, Commented Mar 16, 2013 at 12:14
@Dude According to your comment rule, you will have a forest (multiple trees) of degenerate trees (no branches). Additionally, I can't see any pattern that leads to the result you wrote. I'm not even sure what to ask here to clarify things. — KobeJohn
– KobeJohn, Commented Mar 16, 2013 at 12:27

HYRY · Accepted Answer · 2013-03-16 12:26:16Z

4

If you can use dict only:

l = [[1], [2,3], [2,4], [2,5], [2,5,6], [2,5,7], [2,5,8],[2,5,8,9], [10],[11,12]]
root = {}
for path in l:
    parent = root
    for n in path:
        parent = parent.setdefault(n, {})
import pprint
pprint.pprint(root, width=1)

output:

{1: {},
 2: {3: {},
     4: {},
     5: {6: {},
         7: {},
         8: {9: {}}}},
 10: {},
 11: {12: {}}}

answered Mar 16, 2013 at 12:26

HYRY

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1 Comment

steven Over a year ago

I also have a nested list, I wonder if there is any way to build a tree with this anytree or treelib?

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