flatten.py

j = {
        'a': 1,
        'b': {
            'a': 2,
            'c': "toto",
            'd': [1, 2, 3],
            'e': {
                'd': "hello",
                'x': [{'1': 2}]
                }
            }
        }



def mergeKeys(k1, k2):
    return "%s.%s" % (k1, k2)

def fmapJ(f, d):
    if isinstance(d, list):
        return [f(x) for x in d]
    if isinstance(d, dict):
        return {k: f(v) for (k, v) in d.items()}
    return d

# https://compiletoi.net/garcon-theres-a-catamorphism-in-my-python/
def cata(f, d, fmap):
    return f(fmap(lambda x: cata(f, x, fmap), d))

def merge(k, v):
    if isinstance(v, dict):
        return [(mergeKeys(k, k2), v2) for (k2, v2) in flatten(v).items()]
    else:
        return [(k, v)]

def merge1(k, v):
    if isinstance(v, dict):
        return [(mergeKeys(k, k2), v2) for (k2, v2) in v.items()]
    else:
        return [(k, v)]

def flattenM(d, m):
    if isinstance(d, dict):
        return {k2: v2 for (k, v) in d.items() for (k2, v2) in m(k, v)}
    return d

def flatten(d):
    return flattenM(d, merge)

def flatten1(d):
    return flattenM(d, merge1)

def flattenC(d):
    return cata(flatten1, d, fmapJ)

def mapKeys1(d, f):
    if isinstance(d, dict):
        return {f(k): v for (k, v) in d.items()}
    return d

def mapKeysC(d, f):
    return cata(lambda x: mapKeys1(x, f), d, fmapJ)