Python Basics — Day 13 JSON (JavaScript Object Notation)

01. What is JSON?

• A lightweight data format that is easy to read and write

• Very similar to Python dictionaries

• Widely used for APIs, data storage, and configuration files

{
  "name": "Sabin",
  "age": 30,
  "skills": ["Python", "Flask", "React"]
}

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02. Working with JSON in Python

Python provides the built-in json module for handling JSON.

import json

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03. Converting Between JSON and Python Objects

JSON → Python

import json

data = '{"name": "Sabin", "age": 30}'  # JSON string
py_obj = json.loads(data)              # JSON string → dict
print(py_obj)                          # {'name': 'Sabin', 'age': 30}
print(py_obj["name"])                  # Sabin

Python → JSON

person = {"name": "Sabin", "age": 30}
json_str = json.dumps(person, ensure_ascii=False)
print(json_str)   # {"name": "Sabin", "age": 30}

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04. Reading & Writing JSON Files

Save to File

person = {"name": "Sabin", "age": 30, "skills": ["Python", "Flask"]}

with open("person.json", "w", encoding="utf-8") as f:
    json.dump(person, f, ensure_ascii=False, indent=2)

👉 indent=2 : pretty formatting with indentation
👉 ensure_ascii=False : prevents non-ASCII characters (e.g., Korean) from breaking

Load from File

with open("person.json", "r", encoding="utf-8") as f:
    data = json.load(f)

print(data)           # {'name': 'Sabin', 'age': 30, 'skills': ['Python', 'Flask']}
print(data["skills"]) # ['Python', 'Flask']

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05. JSON with Lists

people = [
    {"name": "Tom", "age": 20},
    {"name": "Anna", "age": 22}
]

with open("people.json", "w", encoding="utf-8") as f:
    json.dump(people, f, ensure_ascii=False, indent=2)

with open("people.json", "r", encoding="utf-8") as f:
    loaded = json.load(f)

print(loaded[0]["name"])  # Tom

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06. Practice Examples

Example 1: Convert Dictionary to JSON String

book = {"title": "Python Basics", "price": 25000}
json_str = json.dumps(book, ensure_ascii=False)
print(json_str)

Example 2: Convert JSON String to Dictionary

json_data = '{"title": "AI Guide", "author": "Sabin"}'
book = json.loads(json_data)
print(book["author"])

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