Hands-on Lab·Python Automation for IT

Python JSON and Nested Data

JSON is what an API returns and what a config file increasingly is. Four functions cover it, and the interesting parts are the edges: sets and dates cannot be encoded at all, dictionary keys always come back as strings so a round trip is not necessarily equal, and reading somebody else's nested response means never assuming a key is present.

Files and Data Formats Guide 12 of 39 Beginner

Control nodeUbuntu 26.04 LTS
Python3.14.4
requests2.34.2
paramiko5.0.0
TimeAbout 18 min

The json module is unchanged across Python 3. json.JSONDecodeError was added in 3.5 and is a subclass of ValueError, so older except ValueError: code still works.

pytest9.1.1
PyYAML6.0.3
boto3 / botocore1.43.78

Everything on this page runs on the control node. Any machine with Python 3 will do.
Server Name	IP Address	OS	Roles	CPU	RAM	HDD
RUNNER01	192.168.0.27	Ubuntu 26.04 LTS	Control node - every script in this path runs here	2 Core	4 GB	50 GB

This guide includes

Use this for API payloads and for config files that are increasingly JSON. This matters because dictionary keys do not survive the round trip - an int key goes in and a string key comes back.

separating the four functions, and seeing what Python types become
meeting the ordinary types with no JSON equivalent, and teaching the encoder about them
finding that dictionary keys do not survive
reading a nested response without crashing on the host that is missing a field
reading a malformed document, and writing one JSON object per line

Before you start

guide 10 - read_text appears throughout.
guide 16 covers the key-collision behaviour this guide runs into.

The four functions, and which is which
What Python types become
And what has no JSON equivalent
Teaching it the types you use
Dictionary keys do not survive
Reading a nested response without crashing on it
And what it does without the default
Malformed JSON, and what the exception tells you
The options worth knowing
One document per line, for logs and streams
What domain 2 asks about this

Official sources

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Python JSON and Nested Data

This guide includes

Before you start

The four functions, and which is which

What Python types become

And what has no JSON equivalent

Teaching it the types you use

Dictionary keys do not survive

Reading a nested response without crashing on it

And what it does without the default

Malformed JSON, and what the exception tells you

The options worth knowing

One document per line, for logs and streams

What domain 2 asks about this

Official sources