How to flatten a nested dictionary?

Question

Is there a native function to flatten a nested dictionary to an output dictionary where keys and values are in this format:

_dict2 = {
  'this.is.an.example': 2,
  'this.is.another.value': 4,
  'this.example.too': 3,
  'example': 'fish'
}

Assuming the dictionary will have several different value types, how should I go about iterating the dictionary?

Yes, it is possible. What have you tried so far? – Jan Vlcinsky Jun 27 '14 at 09:37 — Jan Vlcinsky, Jun 27 '14 at 09:37

Matthew Franglen · Accepted Answer · 2014-06-27T10:03:18.650

4

You want to traverse the dictionary, building the current key and accumulating the flat dictionary. For example:

def flatten(current, key, result):
    if isinstance(current, dict):
        for k in current:
            new_key = "{0}.{1}".format(key, k) if len(key) > 0 else k
            flatten(current[k], new_key, result)
    else:
        result[key] = current
    return result

result = flatten(my_dict, '', {})

Using it:

print(flatten(_dict1, '', {}))

{'this.example.too': 3, 'example': 'fish', 'this.is.another.value': 4, 'this.is.an.example': 2}

edited Jun 27 '14 at 10:03

answered Jun 27 '14 at 09:42

Matthew Franglen

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There's no need to call the `keys` method when iterating over a dictionary. – Cristian Ciupitu Jun 27 '14 at 09:47
i see, "flatten" would have been a better term to describe it. thank you for the example. >learning – zach Jun 27 '14 at 09:48
1

Also `type(current) is dict` could be replaced with `isinstance(current, dict)` to make the code a bit more general purpose making it work with OrderedDict as well. – Cristian Ciupitu Jun 27 '14 at 09:54

How to flatten a nested dictionary?

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