How To Convert A List to A Tree in Python?

Question

How i can represent a tree from a nested list?

L = [['bike', '2 * wheel+1* frame'], ['wheel', '1*rim+1*spoke+1*hub'], ['rim', 60],['spoke', 120]

Tree = ['bike', 2, ['wheel', 1, ['rim', 60], 1, ['spoke', 120], 1, ['hub', 2]]

Explanation :

In this example bike is made from 2 wheels and 1 frames, wheel is made from 1 rim,1spoke and 1 hub ['rim', 60] means that rim's price is 60.

I could not understand how to convert the list to tree.

Answer 1

Here're the steps I'd take:

1. Write a function such that f('2 * wheel+1* frame') == {'wheel': 2, 'frame': 1}

2. Run that function on the entire list to generate

   [
       ('bike', {'wheel': 2, 'frame': 1}),
       ('wheel', {'rim': 1, 'spoke': 1, 'hub': 1}),
       ('rim', 60)
   ]
   

3. Iterate over this list, and change it to:

   [
       ('bike', {
           ('wheel', {
               ('rim', 60): 1,
               ('spoke', ...): 1,
               ('hub', ...): 1
           }): 2,
           ('frame', ...): 1
       })            
   ]
   

   By replacing 'wheel' with ('wheel', {'rim': 1, 'spoke': 1, 'hub': 1}) etc, recursively

4. Munge this tree format into the desired output