Convert Nested Dictionary into Flattened Dictionary in Python

As the world embraces more unstructured data, we come across many formats of data where the data structure can be deeply nested like nested JSONS. Python has the ability to deal with nested data structure by concatenating the inner keys with outer keys to flatten the data. In this article we will take a nested dictionary and flattened it.

Using a recursive approach

In this approach we design a function to recursively process each item in the dictionary. We pass the dictionary, design a place holder for the output dictionary, the key and separator as parameters. We use the isinstance to check if the next item itself is a dictionary and then pass it through the recursive call if it is also a dictionary.

Example

dictA = {
   "id": "0001",
   "name": "hotdog",
   "image":
      {
         "url": "images/0001.jpg",

            "thumbnail":
               {
                  "url": "images/thumbnails/0001.jpg",
                  "height,width": "2x4"
               }
      }
}
def dict_flatten(in_dict, dict_out=None, parent_key=None, separator="_"):
   if dict_out is None:
      dict_out = {}

   for k, v in in_dict.items():
      k = f"{parent_key}{separator}{k}" if parent_key else k
      if isinstance(v, dict):
         dict_flatten(in_dict=v, dict_out=dict_out, parent_key=k)
         continue

      dict_out[k] = v

   return dict_out

final_dict = dict_flatten(dictA)
print(final_dict)

Output

Running the above code gives us the following result −

{
   'id': '0001',
   'name': 'hotdog',
   'image_url': 'images/0001.jpg',
   'image_thumbnail_url': 'images/thumbnails/0001.jpg',
   'image_thumbnail_height,width': '2x4'
}

With cherrypicker

This is a module which can be directly used by giving it the dictionary as input. The default separator is -.

Example

from cherrypicker import CherryPicker

dictA = {
   "id": "0001",
   "name": "hotdog",
   "image":
      {
         "url": "images/0001.jpg",

            "thumbnail":
               {
                  "url": "images/thumbnails/0001.jpg",
                  "height,width": "2x4"
               }
      }
}

picker = CherryPicker(dictA)
print(picker.flatten().get())

Output

Running the above code gives us the following result −

{
   'id': '0001',
   'name': 'hotdog',
   'image_url': 'images/0001.jpg',
   'image_thumbnail_url': 'images/thumbnails/0001.jpg',
   'image_thumbnail_height,
   width': '2x4'
}