How can you implement a simple REST API using Flask?

Question

Anubhav Kumar · Answer

A clean, beginner-friendly explanation and example of how to implement a
simple REST API using Flask.
1. Install Flask
pip install flask
2. Create the app structure
project/
 └── app.py
3. Basic REST API Example (CRUD)
Here is a complete working example that implements:
GET (read all)GET by IDPOST (create)PUT (update)DELETE (remove)
app.py
from flask import Flask, jsonify, request
app = Flask(__name__)
# Fake in-memory database
books = [
    {"id": 1, "title": "Book One", "author": "Author A"},
    {"id": 2, "title": "Book Two", "author": "Author B"},
]
# GET all books
@app.route("/books", methods=["GET"])
def get_books():
    return jsonify(books)
# GET book by ID
@app.route("/books/andlt;int:book_idandgt;", methods=["GET"])
def get_book(book_id):
    book = next((b for b in books if b["id"] == book_id), None)
    return jsonify(book) if book else ("Not Found", 404)
# POST → Create new book
@app.route("/books", methods=["POST"])
def add_book():
    data = request.get_json()
    new_book = {
        "id": books[-1]["id"] + 1 if books else 1,
        "title": data["title"],
        "author": data["author"]
    }
    books.append(new_book)
    return jsonify(new_book), 201
# PUT → Update book
@app.route("/books/andlt;int:book_idandgt;", methods=["PUT"])
def update_book(book_id):
    data = request.get_json()
    book = next((b for b in books if b["id"] == book_id), None)
    if not book:
        return ("Not Found", 404)
    book["title"] = data.get("title", book["title"])
    book["author"] = data.get("author", book["author"])
    return jsonify(book)
# DELETE → Remove book
@app.route("/books/andlt;int:book_idandgt;", methods=["DELETE"])
def delete_book(book_id):
    global books
    books = [b for b in books if b["id"] != book_id]
    return ("Deleted", 204)
if __name__ == "__main__":
    app.run(debug=True)
4. Run the API
python app.py
Flask will start at:
http://127.0.0.1:5000
Test the API using cURL or Postman
GET all
GET http://127.0.0.1:5000/books
POST
POST http://127.0.0.1:5000/books
Content-Type: application/json
{
  "title": "New Book",
  "author": "New Author"
}

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How can you implement a simple REST API using Flask?

Anubhav Kumar

Can you answer this question?

1 Answers

1. Install Flask

2. Create the app structure

3. Basic REST API Example (CRUD)

app.py

4. Run the API

Test the API using cURL or Postman

GET all

POST

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