CODEWITHSUNDEEP
pythonlistpython-3.xtuplesnested-lists
Alshafai
Alshafai

Reputation: 11

Converting a list of tuples to a deep nested list

I have a program that generates the following list of tuples:

[('Government and politics', 2), ('Government', 3), ('Capital punishment', 4), ('Federal representation', 4), ('Politics', 3)]

Where the number reflects the hierarchy. I was wondering if there is a recursive way of converting this list of tuples into a nested list as follows:

['Government and politics', ['Government', ['Capital punishment', 'Federal representation'], 'Politics']]

Upvotes: 1

Views: 96

Answers (1)

schesis
schesis

Reputation: 59178

It's not necessary to use recursion in this case:

def nest(data, base=0):
    result = []
    for item, level in data:
        target = result
        for depth in range(base, level):
            if not (len(target) > 0 and isinstance(target[-1], list)):
                target.append([])
            target = target[-1]
        target.append(item)
    return result

The outer loop of this function iterates over the item, level pairs in your data, and the inner loop drills down to the appropriate depth, creating new sub-lists as necessary as it goes.

The base argument is the minimum level in your data, in this case 2. Here it is in action:

>>> data = [
...     ('Government and politics', 2),
...     ('Government', 3),
...     ('Capital punishment', 4),
...     ('Federal representation', 4),
...     ('Politics', 3)
... ]


>>> nest(data, 2)
['Government and politics', ['Government', ['Capital punishment', 'Federal representation'], 'Politics']]

Upvotes: 2

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