JSON | Python by example

JSON in Python

Python provides the json module to work with JSON data.

Encoding (Python to JSON)

Converting Python objects to JSON strings is called encoding, or serializing, or marshaling. The json module provides two main functions for this: json.dumps() which converts a Python object to a JSON string, and json.dump() which writes JSON data to a file.

import json

# Python dictionary
data = {
    "name": "Alice",
    "age": 30,
    "is_student": False,
    "courses": ["Python", "Data Science", "Web Development"],
    "address": {
        "city": "New York",
        "country": "USA"
    }
}

# Convert Python object to JSON string
json_string = json.dumps(data)
print(json_string)
# Output: {"name": "Alice", "age": 30, "is_student": false, "courses": ["Python", "Data Science", "Web Development"], "address": {"city": "New York", "country": "USA"}}

# Pretty-print with indentation
pretty_json = json.dumps(data, indent=4)
print(pretty_json)
# Output:
# {
#     "name": "Alice",
#     "age": 30,
#     "is_student": false,
#     "courses": [
#         "Python",
#         "Data Science",
#         "Web Development"
#     ],
#     "address": {
#         "city": "New York",
#         "country": "USA"
#     }
# }

# Write JSON to a file
with open('data.json', 'w') as file:
    json.dump(data, file, indent=4)

Decoding (JSON to Python)

Converting JSON strings to Python objects is called decoding, or deserializing, or unmarshaling. The json module provides two main functions for this: json.loads() which converts a JSON string to a Python object, and json.load() which reads JSON data from a file.

import json

# JSON string
json_string = '{"name": "Bob", "age": 25, "is_student": true, "grades": [90, 85, 88]}'

# Convert JSON string to Python object
python_data = json.loads(json_string)
print(python_data)
# Output: {'name': 'Bob', 'age': 25, 'is_student': True, 'grades': [90, 85, 88]}

# Access the data
print(python_data["name"])      # Output: Bob
print(python_data["grades"][0]) # Output: 90

# Read JSON from a file
with open('data.json', 'r') as file:
    file_data = json.load(file)
    print(file_data)

Next example: CSV