Python code examples to flatten a nested dictionary

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The code snippet contains different code examples to flatten a python dictionary. If you are using pandas in your project then you can use the below code.

#Using pandas DataFrame
import pandas as pd

d = {'x': 1,
     'y': {'a': 2, 'b': {'c': 3, 'd' : 4}},
     'z': {'a': 2, 'b': {'c': 3, 'd' : 4}}}

dframe = pd.json_normalize(d, sep='_')

print(dframe.to_dict(orient='records')[0])

Output

{
'x': 1,
'y_a': 2,
'y_b_c': 3,
'y_b_d': 4,
'z_a': 2,
'z_b_c': 3,
'z_b_d': 4
}

A dictionary in python contains one or multiple key-value pair sets of values. It can also be nested and contains multiple sets as a value for a key. You can read more about python dictionaries here.

We are using the pandas json_normalize() method and passing nested dictionary and separator values to flatten the dictionary. After flattening the dictionary we are converting the data frame to dictionary with orientation records.

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flatten a dictionary in python

Flatten dictionary without using any package

def flatten_dict(my_dict, p_val=''):
  final_dict = {}
  for key, val in my_dict.items():
    new_key = p_val + key
    if isinstance(val, dict):
        final_dict.update(flatten_dict(val, new_key + '_'))
    else:
        final_dict[new_key] = val
  return final_dict
  
result = flatten_dict(
  {
    'x': 1,
    'y': {'a': 2, 'b': {'c': 3, 'd' : 4}},
    'z': {'a': 2, 'b': {'c': 3, 'd' : 4}}
  },
  ''
)

print(result)

Here we have created a python function that is not using any dependency package to flatten a python dictionary. The parameters that passed to the function flatten_dict() is the dictionary that you want to flatten

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