Python Intermediate Lesson 8: JSON and APIs

📎 This article includes 3 downloadable practice files ↓

📘 Python Intermediate Course · Lesson 8 of 10

Almost every web service (exchange rates, GST lookups, courier tracking, your own company’s systems) speaks JSON over HTTP.

JSON in Python

import json
data = json.loads(text)            # JSON text -> dict/list
text = json.dumps(data, indent=2)  # dict/list -> JSON text
json.load(open("rates.json"))      # from a file

Calling an API

import requests
r = requests.get("https://api.example.com/rates", params={"base": "INR"}, timeout=10)
r.raise_for_status()               # stop on 4xx/5xx instead of parsing an error page
data = r.json()

The lesson script reads the same structure from rates.json so it runs offline; swap in the two lines above when you have a real API.

Good habits

• Always set a timeout, or a dead server hangs your script forever.
• Keep API keys out of the script: os.environ["RATES_API_KEY"], set once on the PC.
• Respect rate limits; cache responses you reuse (save the JSON with today’s date in the file name).
• Check the fields you need exist: data.get("rates", {}).get("USD").

Practice

Unzip the practice data into a folder, put this lesson’s script in the same folder and run it (python pyi-NN.py). Compare with the expected output file. Then change one thing (a filter, a column, a format) and predict the new output before you run it.