Turning dynamically sized list into tree structured like dictionary-CodePudding

I'm trying to build up an dictionary based on a list with a dynamic size.

parts = [['Sect', 'H1'],
['Sect', 'P'],
['Sect', 'P[2]'],
['Sect[2]', 'Sect', 'H2']]

Should result in such a dictionary like:

{
  "Sect": {
      "H1": {

      },
      "P": {

      },
      "P[2]": {

      },

    },
  "Sect[2]": {
      "Sect": {
        "H2": {

        }
      }
    }
}

I can't get it. Any idea how to turn a list of dynamic size into a tree structured dictionary?

My approach so far:

            for i, part in enumerate(parts):
                if i == 0:
                    if part not in result:
                        result[part] = dict()
                if i == 1:
                    if part not in result[parts[i-1]]:
                        result[parts[i-1]][part] = dict()
                if i == 2:
                    if part not in result[parts[i-2]][parts[i-1]]:
                        result[parts[i-2]][parts[i-1]][part] = dict()
            ...

But this isn't a dynamic approach so far.

CodePudding user response：

Similar to quamrana's answer, but a bit terser with dict.setdefault.

d = {}
for p in parts:
    inner = d
    for k in p:
       inner = inner.setdefault(k, {})

print(d) # {'Sect[2]': {'Sect': {'H2': {}}}, 'Sect': {'P[2]': {}, 'P': {}, 'H1': {}}}

CodePudding user response：

The answer is iteration. You can iterate over a list of lists. And for each list you can iterate to produce hierarchical dicts.

parts = [['Sect', 'H1'],
['Sect', 'P'],
['Sect', 'P[2]'],
['Sect[2]', 'Sect', 'H2']]

data = {}
for part in parts:
    d = data   # refer to a current dict
    for key in part:
        new_dict = d[key] if key in d else {}
        d[key] = new_dict
        d = new_dict   # recurse down the nested dicts
print(data)