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How to Read and Write CSV, JSON and Text Files in Python (with open and with)

P9.5 How to Read and Write JSON Files in Python

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Why. APIs and apps send data as JSON. It looks exactly like Python dictionaries and lists.

What. json.load(f) reads a JSON file into Python. json.dump(data, f) writes Python data as JSON. json.loads(text) / json.dumps(data) work with strings.

How.

Work with JSON

  1. Open the file with utf-8.
  2. Use json.load to read.
  3. Access values like dicts and lists.
  4. Use json.dump(data, f, indent=2) to write a readable file.

Worked example A — Read a JSON file.

Step 1 — What we do. An e-commerce app in Spain exports orders as JSON.

Step 2 — Make the input file orders.json in the same folder as your code:

{"shop": "Madrid Central", "currency": "EUR", "orders": [{"id": "M1", "total": 35.5}, {"id": "M2", "total": 12.0}]}

About this data: the file has the shop name, the currency, and a list of orders. Each order has an id and a total in euros.

Step 3 — Type and run this code.

import json
with open("orders.json", encoding="utf-8") as f:
    data = json.load(f)
print(data["shop"])
for o in data["orders"]:
    print(o["id"], o["total"])

Step 4 — Output you should see.

Madrid Central
M1 35.5
M2 12.0

Step 5 — What it means. JSON objects become dicts and arrays become lists.

Worked example B — Write JSON.

Step 1 — What we do. We save a settings dictionary for a report.

Step 2 — Type and run this code.

import json
settings = {"region": "EU", "currency": "€", "top_n": 5}
with open("settings.json", "w", encoding="utf-8") as f:
    json.dump(settings, f, indent=2, ensure_ascii=False)
print(open("settings.json", encoding="utf-8").read())

Step 3 — Output you should see.

{
  "region": "EU",
  "currency": "€",
  "top_n": 5
}

Step 4 — What it means. indent=2 makes it readable. ensure_ascii=False keeps € as €, not \u20ac.

Python JSON
dict object { }
list array [ ]
str string
int / float number
True / False true / false
None null

How to read this table: each row shows a Python type and what it becomes in JSON.

Ravindra Bagale's Tip

If an API gives nested JSON, look at one record first with print(json.dumps(rec, indent=2)). Then decide which fields you need.