Flattening JSON objects in Python

JSON(JavaScript Object Notation) is a data-interchange format that is human-readable text and is used to transmit data, especially between web applications and servers. The JSON files will be like nested dictionaries in Python. To convert a text file into JSON, there is a json module in Python. This module comes in-built with Python standard modules, so there is no need to install it externally.

A flatten json is nothing but there is no nesting is present and only key-value pairs are present.

Example:

Unflattened JSON:
{‘user’ :{‘Rachel’:{‘UserID’:1717171717,
‘Email’: ‘rachel1999@gmail.com’,
‘friends’: [‘John’, ‘Jeremy’, ‘Emily’]}}}

Flattened JSON:
{‘user_Rachel_friends_2’: ‘Emily’, ‘user_Rachel_friends_0’: ‘John’, ‘user_Rachel_UserID’: 1717171717, ‘user_Rachel_Email’: ‘rachel1999@gmail.com’, ‘user_Rachel_friends_1’: ‘Jeremy’}

Need of flattening JSON

There are many reasons for the need of flattening JSON, such as for a better and understandable view that is there are only key-value pairs are present without any nesting. It also allows for context-specific security and constraints to be implemented in a readable, but in more verbose way.

Approach to flatten JSON

There are many ways to flatten JSON. There is one recursive way and another by using the json-flatten library.

Recursive Approach: Now we can flatten the dictionary array by a recursive approach which is quite easy to understand. The recursive approach is a bit slower than using json-flatten library.

Example:

# for a array value of a key 
unflat_json = {'user' : 
               {'Rachel': 
                {'UserID':1717171717, 
                'Email': 'rachel1999@gmail.com',  
                'friends': ['John', 'Jeremy', 'Emily'] 
                } 
               } 
              } 
  
# Function for flattening  
# json 
def flatten_json(y): 
    out = {} 
  
    def flatten(x, name =''): 
          
        # If the Nested key-value  
        # pair is of dict type 
        if type(x) is dict: 
              
            for a in x: 
                flatten(x[a], name + a + '_') 
                  
        # If the Nested key-value 
        # pair is of list type 
        elif type(x) is list: 
              
            i = 0
              
            for a in x:                 
                flatten(a, name + str(i) + '_') 
                i += 1
        else: 
            out[name[:-1]] = x 
  
    flatten(y) 
    return out 
  
# Driver code 
print(flatten_json(unflat_json)) 

Output :

{‘user_Rachel_friends_2’: ‘Emily’, ‘user_Rachel_friends_0’: ‘John’, ‘user_Rachel_UserID’: 1717171717, ‘user_Rachel_Email’: ‘rachel1999@gmail.com’, ‘user_Rachel_friends_1’: ‘Jeremy’}

Using flatten_json library: json-flatten library provides functions for flattening a JSON object to a single key-value pairs, and unflattening that dictionary back to a JSON object.

Installing library

In order to use the flatten_json library, we need to install this library. flatten_json can be installed by running the following command in the terminal.

pip install json-flatten

Example:

from flatten_json import flatten 
  
unflat_json = {'user' : 
               {'Rachel': 
                {'UserID':1717171717, 
                'Email': 'rachel1999@gmail.com',  
                'friends': ['John', 'Jeremy', 'Emily'] 
                } 
               } 
              } 
  
flat_json = flatten(unflat_json) 
  
print(flat_json) 

Output :

{‘user_Rachel_UserID’: 1717171717, ‘user_Rachel_Email’: ‘rachel1999@gmail.com’, ‘user_Rachel_friends_0’: ‘John’, ‘user_Rachel_friends_1’: ‘Jeremy’, ‘user_Rachel_friends_2’: ‘Emily’}

My Personal Notes

Need of flattening JSON

Approach to flatten JSON

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