How to Parse a JSON String in Python?

You can parse a JSON string in Python using the json.loads() method, which deserializes the JSON string to a Python object. You can use it like so:

import json

data = json.loads('{"name": "John Doe", "age": 29}')

print(data['name']) # "John Doe"
print(data['age']) # 29

To see the types of the decoded objects, you can get the class name of the objects like so:

print(type(data['name']).__name__) # str
print(type(data['age']).__name__) # int

The json.loads() method is able to make the following JSON transformations:

JSON	Python
object	dict
array	list
string	str
number (int)	int
number (real)	float
true	True
false	False
null	None

For example:

import json

data = json.loads('{"foo":"bar"}')

# object -> dict
print(data) # {'foo': 'bar'}
print(type(data).__name__) # dict

import json

data = json.loads('["foo", "bar"]')

# array -> list
print(data) # ['foo', 'bar']
print(type(data).__name__) # list

import json

data = json.loads('{"foo": "bar"}')

# string -> str
print(data['foo']) # 'bar'
print(type(data['foo']).__name__) # str

import json

data = json.loads('{"foo": 2, "bar": 1.5}')

# number (int) -> int
print(data['foo']) # 2
print(type(data['foo']).__name__) # int

# number (real) -> float
print(data['bar']) # 1.5
print(type(data['bar']).__name__) # float

import json

data = json.loads('{"foo": true, "bar": false}')

# true -> True
print(data['foo']) # True
print(type(data['foo']).__name__) # bool

# false -> False
print(data['bar']) # False
print(type(data['bar']).__name__) # bool

import json

data = json.loads('{"foo": null}')

# null -> None
print(data['foo']) # None
print(type(data['foo']).__name__) # NoneType

In addition to these, Python is also able to decode NaN, Infinity and -Infinity (even though they're not valid JSON):

JSON	Python
NaN	nan
Infinity	inf
-Infinity	-inf

For example:

import json

data = json.loads('{"foo": NaN, "bar": Infinity, "baz": -Infinity}')

# NaN -> nan
print(data['foo']) # nan
print(type(data['foo']).__name__) # float

# Infinity -> inf
print(data['bar']) # inf
print(type(data['bar']).__name__) # float

# -Infinity -> -inf
print(data['baz']) # -inf
print(type(data['baz']).__name__) # float