Flatten Nested Dictionary within list or having list items. #flatten #python

flatten.py

"""
Using a generator we can `yield` key and value pairs when the value is not an instance of `list` or `dict` 
else we recursively call the function to flatten the object. To preserve empty `list` and `dict` 
we add additional check on obj when checking the obj type.
"""


def flatten(obj, prefix=[], sep="_"):
    if isinstance(obj, list) and obj:
        for i, o in enumerate(obj):
            yield from flatten(o, prefix=prefix + [str(i)], sep=sep)
    elif isinstance(obj, dict) and obj:
        for k, v in obj.items():
            yield from flatten(v, prefix=prefix + [k], sep=sep)
    else:
        yield (sep.join(prefix), obj)

obj = [
    {
        "a": {"b": 1, "c": 2},
        "d": [3, 4, 5],
        "e": {"f": True, "g": False},
        "h": [{"i": 6, "j": 7}, {"i": 8, "j": 9}, {"i": 10, "j": 11}],
        "k" : {"a":{}}
    }
]

print(dict(flatten(obj, sep="_")))
"""
Output:
{'0_a_b': 1,
 '0_a_c': 2,
 '0_d_0': 3,
 '0_d_1': 4,
 '0_d_2': 5,
 '0_e_f': True,
 '0_e_g': False,
 '0_h_0_i': 6,
 '0_h_0_j': 7,
 '0_h_1_i': 8,
 '0_h_1_j': 9,
 '0_h_2_i': 10,
 '0_h_2_j': 11,
 '0_k_a': {}}

Note: This code snippet assumes that the keys will be of type `str`.
"""