JSON Pretty Print using Python

JSON (JavaScript Object Notation) is a text-based data format that is interchangeable with many programming languages. It is commonly used for data transmission between client-server applications. Usually, minified versions of JSON text are transmitted to save bandwidth. However, for debugging and analysis, a beautified version or a pretty print of JSON is required. Essentially, pretty-printing JSON means having proper indentation, white spaces, and separators. 

Example:

Input:
'[ {"studentid": 1, "name": "ABC", "subjects": ["Python", "Data Structures"]}]'
                
Output:

[
   {
       "studentid": 1,
       "name": "ABC",
       "subjects": 
       [
           "Python",
           "Data Structures"
       ]
   }
]

Syntax of json.dumps()

First, use json.loads() method to convert JSON String to Python object. To convert this object to a pretty print JSON string, the json.dumps() method is used. Below are examples and steps to better understand these cases.

Syntax: json.dumps(obj, indent,separator)

Parameter:

• obj: Serialize obj as a JSON formatted stream
• indent: If indent is a non-negative integer or string, then JSON array elements and object members will be pretty-printed with that indent level. An indent level of 0, negative, or “” will only insert newlines.
• separators : If specified, separators should be an (item_separator, key_separator) tuple. 

Pretty Print JSON String

Example 1

This method has the parameter indent to specify the number of spaces and a separator parameter to specify the separator between key and value. By default, the separator is a comma between key-value pairs and a colon between key and value. If the indent parameter of json.dumps() is negative, 0, or an empty string then there are no indentations and only newlines are inserted. By default, the indent is None and the data is represented in a single line.

Python3

# Import required libraries
import json

# Initialize JSON data
json_data = '[ {"studentid": 1, "name": "ABC", \
"subjects": ["Python", "Data Structures"]}, \
                {"studentid": 2, "name": "PQR",\
                "subjects": ["Java", "Operating System"]} ]'

# Create Python object from JSON string data
obj = json.loads(json_data)

# Pretty Print JSON
json_formatted_str = json.dumps(obj, indent=4)
print(json_formatted_str)

Output:

[
   {
       "studentid": 1,
       "name": "ABC",
       "subjects": [
           "Python",
           "Data Structures"
       ]
   },
   {
       "studentid": 2,
       "name": "PQR",
       "subjects": [
           "Java",
           "Operating System"
       ]
   }
]

Example 2

Pretty-Printed JSON data into a file with indent=0.

Python3

# Import required libraries
import json

# Initialize JSON data
json_data = '[ {"studentid": 1, "name": "ABC", \
    "subjects": ["Python", "Data Structures"]},\
    {"studentid": 2, "name": "PQR", \
    "subjects": ["Java", "Operating System"]} ]'

# Create Python object from JSON string data
obj = json.loads(json_data)

# Pretty Print JSON
json_formatted_str = json.dumps(obj, indent=0)
print(json_formatted_str)

Output:

[
{
"studentid": 1,
"name": "ABC",
"subjects": [
"Python",
"Data Structures"
]
},
{
"studentid": 2,
"name": "PQR",
"subjects": [
"Java",
"Operating System"
]
}
]

Write Pretty Print JSON data to file

To write a Python object as JSON formatted data into a file, json.dump() method is used. Like json.dumps() method, it has the indents and separator parameters to write beautified JSON.

Python3

# Import required libraries
import json

data = [{"studentid": 1, "name": "ABC",
         "subjects": ["Python", "Data Structures"]},
        {"studentid": 2, "name": "PQR",
         "subjects": ["Java", "Operating System"]}]

# Write pretty print JSON data to file
with open("filename.json", "w") as write_file:
    json.dump(data, write_file, indent=4)

Output:

filename.json

Read JSON data and pretty print it

Example 1

To read JSON from a file or URL, use json.load(). Then use json.dumps() to convert the object (obtained from reading the file) into a pretty print JSON string. 

Python3

# Import required libraries
import json

# Read JSON data from file and pretty print it
with open("filename.json", "r") as read_file:
    # Convert JSON file to Python Types
    obj = json.load(read_file)

    # Pretty print JSON data
    pretty_json = json.dumps(obj, indent=4)
    print(pretty_json)

Output:

[
   {
       "studentid": 1,
       "name": "ABC",
       "subjects": [
           "Python",
           "Data Structures"
       ]
   },
   {
       "studentid": 2,
       "name": "PQR",
       "subjects": [
           "Java",
           "Operating System"
       ]
   }
]

Example 2

Here we are using pprint module to pretty-print JSON to print our JSON format.

Python3

import json
import pprint

with open("test.json", "r") as json_data:
    student = json.load(json_data)
    print(student)

    print("\n")

# construct PrettyPrinter first
pp = pprint.PrettyPrinter(indent=2, width=30, compact=True)

print("Pretty Printing using pprint module")
pp.pprint(student)

Output:

{'Teacher_id': 1, 'name': 'Suraj', 'Salary': 50000, 'attendance': 80, 
'Branch': ['English', 'Geometry', 'Physics', 'World History'], 'email': 'test@example.com'}


Pretty Printing using pprint module
("{'Teacher_id': 1, 'name': "
 "'Suraj', 'Salary': 50000, "
 "'attendance': 80, "
 "'Branch': ['English', "
 "'Geometry', 'Physics', "
 "'World History'], 'email': "
 "'test@example.com'}")

Pretty-print JSON from the command line

In this example, we are trying to print data using the command line. To validate and pretty-print JSON objects from the command line, Python offers the json.tool package.

Python3

echo {"studentid": 1, "name": "ABC",
      "subjects": ["Python", "Data Structures"]} | python -m json.tool

Output:

{
    "studentid": 1,
    "name": "ABC",
    "subjects": [
        "Python",
        "Data Structures"
    ]
}