creates a tree. Each item (the things with "name") can be in multiple paths. Imagine it like a tree for a media collection with nested tags – every photo can have multiple (nested) tags

treecreator.py

'''
The function call behaviour seems to be identical to the javascript version; I could not find any differences
However, the resulting tree is not identical, the javascript version "reuses" the paths, 
whereas the python one seems to create a new path on every occasion.  

'''
#following adapted from https://stackoverflow.com/a/44185784/263398 and ported to Python

from functools import reduce

data2 = [{
        "name": "Children C1",
        "paths": [["A", "B", "C"],["A", "B"]]
    }, {
        "name": "Children C2",
        "paths": [["A", "B", "C"]]
    }, {
        "name": "Children C3",
        "paths": [["A", "B", "C"]]
    }, {
        "name": "Children B1",
        "paths": [["A", "B"],["C"]]
    }, {
        "name": "Children B2",
        "paths": [["A", "B"],["D", "E"],["X"]]
    }, {
        "name": "Children A1",
        "paths": [["A"],["B"]]
    }, {
        "name": "Children E1",
        "paths": [["D", "E"],["A", "B"]]
    }];

def constructTree(commentsArray):
    result = []

    initialValue = {
        "_":result
    }

    def reducerfunction(accumulator,pathpart):
        print("pathpart", pathpart)
        if not pathpart in accumulator:
            print("IF!")
            accumulator[pathpart] = {
                "_":[]
            }
        accumulator["_"].append({
                "name":pathpart,
                "children":accumulator[pathpart]["_"]
            })
        print("accumulator")
        return accumulator[pathpart]

    for comment in commentsArray:
        for path in comment["paths"]:
            print(path)
            reduce(reducerfunction ,path+[comment["name"]],initialValue)

    return result

tree = constructTree(data2)