1. Parsing JSON Strings in Python (`json.loads`)

To convert a JSON string into a native Python dictionary or list, use `json.loads()` ("load string"). Python automatically converts JSON numbers to `int`/`float`, JSON booleans to `bool`, and JSON `null` to `None`.

Parsing JSON String to Python Dict 
import json

json_string = '{"name": "Alice", "role": "admin", "active": true, "score": null}'

# Parse JSON string into Python dictionary
data = json.loads(json_string)

print(type(data))  # <class 'dict'>
print(data["name"])  # Alice
print(data["active"])  # True (converted to Python bool)
print(data["score"])  # None (converted to Python None)

Explanation: `json.loads()` converts valid JSON strings into Python data types automatically.

Pro Tips

  • Use `json.load(file_object)` when reading directly from a `.json` file on disk.
  • Always wrap `json.loads()` in a `try-except json.JSONDecodeError` block to handle invalid JSON syntax safely.

2. Pretty Printing JSON in Python (`json.dumps`)

To format a Python dictionary into a human-readable, indented JSON string, pass `indent=2` or `indent=4` to `json.dumps()` ("dump string"). Use `sort_keys=True` to order keys alphabetically.

Formatting Python Dict to 2-Space Indented JSON 
import json

user_data = {
    "id": 101,
    "username": "dev_expert",
    "permissions": ["read", "write", "execute"],
    "settings": {"theme": "dark", "notifications": True}
}

# Pretty print JSON string with 2 spaces and sorted keys
pretty_json = json.dumps(user_data, indent=2, sort_keys=True)

print(pretty_json)

Explanation: `json.dumps(obj, indent=2)` turns a Python dictionary into a formatted JSON string.

Pro Tips

  • Set `separators=(",", ": ")` to remove trailing spaces after colons for cleaner logs.
  • For minified JSON output in Python, set `separators=(",", ":")` with zero indent.

3. Handling Python `datetime` Serialization Errors

Python's built-in `json.dumps()` raises a `TypeError: Object of type datetime is not serializable` when trying to serialize `datetime` objects directly. Pass a custom `default` converter function to resolve this.

Serializing Python datetime Objects to JSON 
import json
from datetime import datetime

payload = {
    "event": "user_login",
    "timestamp": datetime.now()
}

# Custom serializer for non-standard objects
def json_serializer(obj):
    if isinstance(obj, datetime):
        return obj.isoformat()
    raise TypeError(f"Type {type(obj)} not serializable")

# Dump JSON using custom default handler
json_output = json.dumps(payload, default=json_serializer, indent=2)

print(json_output)

Explanation: Passing `default=json_serializer` allows Python to convert custom objects like `datetime` into ISO 8601 strings.