Flatten nested dictionaries, compressing keys

Question

Suppose you have a dictionary like:

{\'a\': 1,
 \'c\': {\'a\': 2,
       \'b\': {\'x\': 5,
             \'y\' : 10}},
 \'d\': [1, 2, 3]}

Ho

Answer 1

If you do not mind recursive functions, here is a solution. I have also taken the liberty to include an exclusion-parameter in case there are one or more values you wish to maintain.

Code:

def flatten_dict(dictionary, exclude = [], delimiter ='_'):
    flat_dict = dict()
    for key, value in dictionary.items():
        if isinstance(value, dict) and key not in exclude:
            flatten_value_dict = flatten_dict(value, exclude, delimiter)
            for k, v in flatten_value_dict.items():
                flat_dict[f"{key}{delimiter}{k}"] = v
        else:
            flat_dict[key] = value
    return flat_dict

Usage:

d = {'a':1, 'b':[1, 2], 'c':3, 'd':{'a':4, 'b':{'a':7, 'b':8}, 'c':6}, 'e':{'a':1,'b':2}}
flat_d = flatten_dict(dictionary=d, exclude=['e'], delimiter='.')
print(flat_d)

Output:

{'a': 1, 'b': [1, 2], 'c': 3, 'd.a': 4, 'd.b.a': 7, 'd.b.b': 8, 'd.c': 6, 'e': {'a': 1, 'b': 2}}