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

Here's an algorithm for elegant, in-place replacement. Tested with Python 2.7 and Python 3.5. Using the dot character as a separator.

def flatten_json(json):
    if type(json) == dict:
        for k, v in list(json.items()):
            if type(v) == dict:
                flatten_json(v)
                json.pop(k)
                for k2, v2 in v.items():
                    json[k+"."+k2] = v2

Example:

d = {'a': {'b': 'c'}}                   
flatten_json(d)
print(d)
unflatten_json(d)
print(d)

Output:

{'a.b': 'c'}
{'a': {'b': 'c'}}

I published this code here along with the matching unflatten_json function.