Python JSON for Beginners

JSON is a text format for structured data. APIs and configuration files use it constantly. Python's json module converts between JSON text and dictionaries, lists, strings, numbers, booleans, and None. You will also validate decoded JSON before indexing and produce stable output.

Parse and serialise

json.loads(text) parses a JSON string into Python values. json.dumps(value) turns a Python value into JSON text. The s in loads and dumps stands for string; load and dump work with file objects.

import json
raw = '{"drink": "latte", "price": 4.5}'
data = json.loads(raw)
print(data["drink"])
print(json.dumps(data))

Text to Python and back

Walk nested data

A JSON object becomes a dictionary; a JSON array becomes a list. Chain keys and indexes to reach a nested value. Loop over a list of records when you need to summarise every item.

import json
raw = '{"items": [{"name": "latte"}, {"name": "tea"}]}'
data = json.loads(raw)
for item in data["items"]:
    print(item["name"])

Nested records

Keep output readable

json.dumps accepts indent for pretty printing and sort_keys for stable key order. These options are useful for configuration files and debugging. They do not change the underlying values.

import json
data = {"b": 2, "a": 1}
print(json.dumps(data, indent=2, sort_keys=True))

Readable JSON

Validate shape before indexing

json.loads() validates JSON syntax, not your schema. A decoded value can be a list instead of a dictionary, or a field can be missing. Check the container type, then each key, before indexing.

import json
raw = '{"order": {"items": [{"name": "latte", "qty": 2}]}}'
data = json.loads(raw)
order = data.get("order", {})
items = order.get("items", [])
print(isinstance(items, list), len(items))
if items and isinstance(items[0], dict):
    print(items[0].get("name", "unknown"))

Syntax is not a schema

Make JSON output stable

sort_keys=True makes output stable across runs, and indent=2 makes it readable. Use compact output for machines and indented output for logs or teaching examples. ensure_ascii=False keeps non-English text readable when that is desired.

import json
payload = {"total": 12.0, "items": ["latte", "tea"], "note": "café"}
print(json.dumps(payload, sort_keys=True))
print(json.dumps(payload, indent=2, sort_keys=True, ensure_ascii=False))

Stable key order and readable Unicode

JSON is not Python

JSON supports objects, arrays, strings, numbers, booleans, and null. Python tuples become arrays, integer keys become strings, and None becomes null. That means a round trip may not preserve the original Python types. Dump with sort_keys=True for stable output, and use ensure_ascii=False when you want readable non-ASCII text.

import json

payload = {"count": 2, "tags": ("tea", "latte"), "note": None}
text = json.dumps(payload, sort_keys=True)
print(text)
print(json.loads(text))

A tuple becomes an array

Try it yourself

Change the values, predict the output, then run the code. The Python runtime is downloaded the first time you press Run, so the first run can take a few seconds.