Activity: Writing your first prompts

• Add features, add features to a basic codebase using comments (e.g., add user input, simple calculations).
• Fix bugs, let's fix a bug in the codebase using Copilot's suggestions.
• Refactor, let's improve a codebase using Copilot's suggestions.

Add features

Let's take this REST API and add more features to it. The API manages your product catalog:

from flask import Flask, jsonify, request

products = [
    {'id': 1, 'name': 'Product 1', 'price': 10.0},
    {'id': 2, 'name': 'Product 2', 'price': 20.0},
    {'id': 3, 'name': 'Product 3', 'price': 30.0},
    {'id': 4, 'name': 'Product 4', 'price': 40.0},
    {'id': 5, 'name': 'Product 5', 'price': 50.0},
    {'id': 6, 'name': 'Product 6', 'price': 60.0},
    {'id': 7, 'name': 'Product 7', 'price': 70.0},
    {'id': 8, 'name': 'Product 8', 'price': 80.0},
    {'id': 9, 'name': 'Product 9', 'price': 90.0},
    {'id': 10, 'name': 'Product 10', 'price': 100.0}
]

## add routes
@app.route('/products', methods=['GET'])
def get_products():
    return jsonify(products)

@app.route('/products/<int:product_id>', methods=['GET'])
def get_product(product_id):
    product = next((p for p in products if p['id'] == product_id), None)
    return jsonify(product) if product else ('', 404)

## create a Flask app
app = Flask(__name__)

Task: Write a prompt to support pagination, client should be able to specify the page and the number of items per page. The API should return a paginated list of products.

1. Try typing it as a comment directly in a code file. For example:

# Add pagination to the /products endpoint. The client should be able to specify the page and the number of items per page. The API should return a paginated list of products.

1. Try the same comment in the chat interface.

Refactor

Refactor the code to something you want to maintain, i.e a class-based approach where responsibilities are separated. For example, you can create a Product class and a ProductService class to handle the business logic. You can also create a ProductController class to handle the API endpoints.

1. Use the chat interface for this.

Suggested prompts:

• Refactor the code to use a class-based approach and separating concerns.

Fix a bug

# write a function below that takes a cart of products and applies a discount of 3 for 2, i.e buy 3 and pay for 2, choose the cheapest one to be free. However, there should be a bug that takes away the last product from the cart total.

def apply_discount(cart):
    cart.sort(key=lambda x: x['price'])
    total = 0
    for i in range(len(cart)):
        if i % 3 == 2:
            continue
        total += cart[i]['price']
    return total

Here's the test file:

import unittest

from app import apply_discount

class TestApplyDiscount(unittest.TestCase):
    def test_apply_discount(self):
        cart = [
            {'id': 1, 'name': 'Product 1', 'price': 10.0},
            {'id': 2, 'name': 'Product 2', 'price': 20.0},
            {'id': 3, 'name': 'Product 3', 'price': 30.0},
            {'id': 4, 'name': 'Product 4', 'price': 40.0},
            {'id': 5, 'name': 'Product 5', 'price': 50.0}
        ]
        self.assertEqual(apply_discount(cart), 140.0) # i.e the cheapest one, 10.0 should be free, total without discount is 150.0

Suggested prompts:

• What does this code do?
• Change it to "behavior"

Optional: Improve security

The idea here is to make the API more secure. Ask Copilot to consider how to make the code more secure.

Suggested prompts:

• How would you make this code more secure?
• Add authentication to the API.
• Add authorization to the API.