APIs and JSON

HTTP from both sides: calling APIs and validating what comes back, then building, documenting and hosting an API of your own.

Complete 18 notebooks 18 written

Before this guide: Python from the Start; Files, Paths and Formats; and Object-Oriented Python.

The notebooks

Open in Colab runs a notebook in your browser, and Read shows it on GitHub without running it. Every notebook runs on its own, and the answers to its exercises are in a separate notebook, linked as Solutions.

1	What an API IsRequests, responses, methods, parameters and status codes: the vocabulary of every API	Open in Colab Read Solutions
2	Exploring an APIPostman, curl and interactive docs, and reading an API's documentation before writing code	Open in Colab Read Solutions
3	Your First Requestrequests.get, and everything the response object carries	Open in Colab Read Solutions
4	Status Codes200, 404, 429, 500, and what your code should do about each	Open in Colab Read Solutions
5	Query ParametersThe params argument, encoding, and building a URL correctly	Open in Colab Read Solutions
6	JSON in a ResponseParsing, nested structures, and reaching the field you want	Open in Colab Read Solutions
7	Schemas and ValidationJSON Schema, Pydantic, and a clear error when a response changes shape	Open in Colab Read Solutions
8	Headers and Content TypesWhat you sent, what came back, and why it matters	Open in Colab Read Solutions
9	AuthenticationAPI keys, bearer tokens, and never committing either	Open in Colab Read Solutions
10	PaginationCursors, page numbers, and a loop that terminates	Open in Colab Read Solutions
11	Rate Limits429, backoff, and being a good citizen of someone else's server	Open in Colab Read Solutions
12	Errors and RetriesTimeouts, connection failures, and what is worth retrying	Open in Colab Read Solutions
13	Sending DataPOST, PUT, DELETE, and what idempotent means in practice	Open in Colab Read Solutions
14	A Real ClientOne API wrapped in a small, testable module you would reuse	Open in Colab Read Solutions
15	Your First API ServerFastAPI, a route, and the documentation it writes for you	Open in Colab Read Solutions
16	Validating RequestsPydantic models on the server, and a 422 with a reason for bad input	Open in Colab Read Solutions
17	A Complete APIThe practice API rebuilt in FastAPI, with every method and the status codes a server chooses	Open in Colab Read Solutions
18	Hosting an APIFrom Colab to a public URL: a start command, secrets, and a free host	Open in Colab Read Solutions

Sources

The real-API examples use weather data from Open-Meteo.com, offered under a CC BY 4.0 license and drawn from the ERA5 reanalysis. Generated using Copernicus Climate Change Service information 2026. Everything else these notebooks request comes from a practice API written for this guide.