json - JSON Encoder and Decoder

JSON encoding and decoding

The json module provides functions for encoding and decoding JSON data.

Module Import

import json

Encoding (Python to JSON)

dumps() - Serialize to String

import json

data = {
    'name': 'Alice',
    'age': 30,
    'city': 'NYC',
    'hobbies': ['reading', 'coding']
}

# Convert to JSON string
json_string = json.dumps(data)
print(json_string)
# '{"name": "Alice", "age": 30, "city": "NYC", "hobbies": ["reading", "coding"]}'

# Pretty print
json_string = json.dumps(data, indent=2)
print(json_string)
# {
#   "name": "Alice",
#   "age": 30,
#   ...
# }

dump() - Write to File

import json

data = {'name': 'Alice', 'age': 30}

with open('data.json', 'w') as f:
    json.dump(data, f, indent=2)

Decoding (JSON to Python)

loads() - Parse String

import json

json_string = '{"name": "Alice", "age": 30}'
data = json.loads(json_string)
print(data)  # {'name': 'Alice', 'age': 30}
print(data['name'])  # 'Alice'

load() - Read from File

import json

with open('data.json', 'r') as f:
    data = json.load(f)
print(data)

Type Mapping

Python	JSON
dict	object
list, tuple	array
str	string
int, float	number
True	true
False	false
None	null

Options

import json

data = {'name': 'Alice', 'items': [1, 2, 3]}

# Compact output
json.dumps(data, separators=(',', ':'))
# '{"name":"Alice","items":[1,2,3]}'

# Sort keys
json.dumps(data, sort_keys=True)

# Handle non-serializable objects
import datetime

def serialize_datetime(obj):
    if isinstance(obj, datetime.datetime):
        return obj.isoformat()
    raise TypeError(f"Type {type(obj)} not serializable")

data = {'timestamp': datetime.datetime.now()}
json.dumps(data, default=serialize_datetime)

Practical Examples

Config File

import json

config = {
    'database': {
        'host': 'localhost',
        'port': 5432,
        'name': 'mydb'
    },
    'debug': True
}

# Save config
with open('config.json', 'w') as f:
    json.dump(config, f, indent=2)

# Load config
with open('config.json', 'r') as f:
    config = json.load(f)

API Response

import json

# Parse API response
response_text = '{"status": "success", "data": {"id": 1, "name": "Item"}}'
response = json.loads(response_text)

if response['status'] == 'success':
    print(f"Item: {response['data']['name']}")

pickle

Python object serialization

csv

CSV file handling