Python: create tree structure from given array/list

Question

I ended up into a problem.

Let's say i have a given array, or 4 separate lists( the columns )

P1 L1 V1 O1

P1 L1 V1 O2

P1 L1 V2 O1 

P1 L1 V3 O3

P2 L1 V2 O1
 
P2 L2 V1 O2

P2 L3 V4 O2

I would like to transform this into a python tree structure:

P1|

  |L1|

     |V1|

     |   |O1

     |   |O2

     |   |O3

     |V2|

     |  |O1

     |V3|

        |O3

P2|

  |L1|V2|O1

  |L2|V1|O2

  |L3|V4|O2

Ok now, this given array can change depending on the user input, it will always have this "kind of structure", but it's not defined a priori.

My goal is to define such a structure and have the possibility to know all the parents of a given children at the lowest level.

To sum up, as suggested from @trincot I enter an input/output data type:

Input: 4 lists, example:
['P1', 'P1', 'P1', 'P1', 'P1', 'P1', 'P1', 'P1', 'P1', 'P1', 'P1', 'P1', 'P2', 'P2', 'P2', 'P2', 'P2', 'P2', 'P2', 'P2', 'P2', 'P2']

output: One tree structure like this:
{'P1': {'L1': {'V1': {'O1': 'O1'}}, 'L2': {'V2': {'O2': 'O2'}, 'V1': {'O1': 'O1'}}}, 'P2': {'L1': {'V1': {'O1': 'O1'}}, 'L2': {'V2': {'O2': 'O2'}, 'V1': {'O1': 'O1'}}}}

In the output I would like then to know at last level what are the elements and know all the parents of this element.

Of course if another data type is more appropriate I would appreciate any suggestion.

Thanks for your help!

Please provide your input in the exact data structure you have for it, and the exact output structure (in Python syntax) you expect for it. — trincot, Oct 14 '21 at 21:47
My input would be a a 4 lists containing the P, L, V, O. My output would be a tree structure like: P1{L1{V1{O1,O2,O3} , V2{O1, O2}}, {L2 {.....}}, ....} — Andrea T, Oct 15 '21 at 08:26
Please edit your question and add this input/output in Python syntax, not (only) as an English description which can be ambiguous. — trincot, Oct 15 '21 at 08:50
Is that example input related to the example input? Can you make them relate to eachother, so there is an actual test case to be made? — trincot, Oct 15 '21 at 13:03

trincot · Accepted Answer · 2021-10-18T10:10:50.293

I didn't see the connection between example input and example output, so I'm going to take a guess at what you want.

Here is an implementation:

# sample input
data = [
    ['P1', 'P1', 'P1', 'P1', 'P2', 'P2', 'P2'],
    ['L1', 'L1', 'L1', 'L1', 'L1', 'L2', 'L3'],
    ['V1', 'V1', 'V2', 'V3', 'V2', 'V1', 'V4'],
    ['O1', 'O2', 'O1', 'O3', 'O1', 'O2', 'O2']
]

forest = {}
for *path, last in zip(*data):
    node = forest
    for code in path:
        node = node.setdefault(code, {})
    node[last] = last

After running this code, forest will be the following nested dictionary:

{
  "P1": {
    "L1": {
      "V1": {
        "O1": "O1",
        "O2": "O2"
      },
      "V2": {
        "O1": "O1"
      },
      "V3": {
        "O3": "O3"
      }
    }
  },
  "P2": {
    "L1": {
      "V2": {
        "O1": "O1"
      }
    },
    "L2": {
      "V1": {
        "O2": "O2"
      }
    },
    "L3": {
      "V4": {
        "O2": "O2"
      }
    }
  }
}

Hi,thanks for the help. yes this kind of I am looking for. Just 2 questions: 1) can you explain me the "node = tree" in your code where dowas tree come from? And how forest is related to the rest of the code? I do not see any call to this object — Andrea T, Oct 18 '21 at 09:29
Ah that is a name change I did at the last moment and turns out I forgot one change. Now updated: there should be no `tree` variable. — trincot, Oct 18 '21 at 10:09

Python: create tree structure from given array/list

1 Answers1