List of tuples of arbitrary length to nested dictionary

Question

So I have a list of tuples of the form:

my_list=[('a','aa','aaa',0),('a','aa','aab',1),('a','ab','aba',2)]

And I need it to convert it to a nested dictionary:

out={'a':{'aa':{'aaa':0,'aab':1},'ab':{'aba':2}}}

The crucial piece of my setting is that I do not know in advance the length of the tuples in my_list (4 is just an example). Is there an easy way to generalize the cases I saw in other answers (e.g. Python list of tuples to nested dict or Convert a list of variable length Tuples into Dictionary) beyond the fixed 3-element tuples they use?

I made various attempts with recursive functions but I do not have anything close to a solution.

Asked By: Thanatopseustes

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Source

Answer 1

Just loop over the first keys, setting aside the last pair of items which will be a key-value pair, and set dictionaries in-between (using setdefault here, but you could do that part manually):

result = {}
for *keys, last_key, value in my_list:
    current = result
    for key in keys:
        current = current.setdefault(key, {})
    current[last_key] = value

Just to be explicit by what I mean by "manually" (I guess I should rather say "explicitly"):

result = {}
for *keys, last_key, value in my_list:
    current = result
    for key in keys:
        if key not in current:
            current[key] = {}
        current = current[key]
    current[last_key] = value

Answered By: juanpa.arrivillaga

List of tuples of arbitrary length to nested dictionary

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