json.dumps() / json.loads()

import json

# Convert a Python object to a JSON string.
json_str = json.dumps(object, ensure_ascii=False, indent=2)

# Convert a JSON string to a Python object.
obj = json.loads(json_str)

# Write a Python object to a JSON file.
with open('data.json', 'w', encoding='utf-8') as f:
    json.dump(object, f, ensure_ascii=False, indent=2)

# Read a JSON file and convert it to a Python object.
with open('data.json', 'r', encoding='utf-8') as f:
    obj = json.load(f)

import json

# Use dumps() to convert a Python dict to a JSON string.
user = {'name': 'Alice', 'age': 30, 'active': True, 'score': None}
json_str = json.dumps(user, ensure_ascii=False)
print(json_str)
# Outputs: '{"name": "Alice", "age": 30, "active": true, "score": null}'

# Omitting ensure_ascii=False escapes non-ASCII characters.
print(json.dumps({'name': 'Tanaka Taro'}))
# Outputs: '{"name": "Tanaka Taro"}'

# Use indent to pretty-print the output.
pretty = json.dumps(user, ensure_ascii=False, indent=2)
print(pretty)
# Outputs the JSON formatted with indentation for readability.

# Use loads() to convert a JSON string to a Python object.
json_text = '{"title": "Python Basics", "pages": 300, "tags": ["beginner", "programming"]}'
data = json.loads(json_text)
print(data['title'])     # Outputs: 'Python Basics'
print(data['tags'][0])   # Outputs: 'beginner'

# Use dump() to write to a file.
config = {'host': 'localhost', 'port': 8080, 'debug': False}
with open('config.json', 'w', encoding='utf-8') as f:
    json.dump(config, f, ensure_ascii=False, indent=2)

# Use load() to read from a file.
with open('config.json', 'r', encoding='utf-8') as f:
    loaded = json.load(f)
print(loaded['port'])  # Outputs: 8080

# An invalid JSON string raises an error.
try:
    json.loads("{'key': 'value'}")  # Single quotes are not valid JSON.
except json.JSONDecodeError as e:
    print(f'JSON error: {e}')

json.dumps() converts to an in-memory string, while json.dump() writes directly to a file. Similarly, json.loads() converts from a string, and json.load() reads from a file. A helpful way to remember the difference is that the trailing s stands for "string".

The type mapping between Python and JSON is as follows: Python dict → JSON object, list/tuple → JSON array, str → JSON string, int/float → JSON number, True/False → true/false, None → null.

When working with data that contains non-ASCII characters, always specify ensure_ascii=False. With the default setting (ensure_ascii=True), non-ASCII characters are escaped to \uXXXX sequences, which increases file size and reduces readability.