Python Classroom notes 10/Sep/2024

Web applications and different hosting platforms

• Web Applications are hosted on www and they respond to requests from browsers
• Web Applications initially were only expected to serve html content i.e it was enough to create static pages. Techonology
  • html
  • css
  • javascript
  • (asp/javscript)
• Then web applications were supposed to be interactive handling business logics such as ticket booking, online transfers, then the earlier technologies cannot handle this, then application servers started evolving.
  • java: j2ee, servlets, jsp, spring mvc
  • dotnet: asp.net
  • ruby: ruby on rails
  • php
  • python: django
  • nodejs
    
• Then sepeartion of web and business logic was the next step
  • web layer (html):
    • vanila javascript
    • angular js
    • react js
    • vue js
  • app layer (business logic)
  • db layer
    
• Then to individual scale and for easier deployments without having downtimes, microservices were introducted

Hosting Platforms

• Deploying python web apps or apis
  • Physical server
  • Virtual Servers (AWS/Azure/GCP/VmWare) (IaaS)
  • Platform as a Service (PaaS)
  • Container (Docker, Kuberentes)
• To deploy web apis we can use serverless in addition to all of the above
  

REST API

• HTTP is a popular protocol which responds to client request serving content
• HTTP Methods
  
• HTTP Status code Refer Here
  
• Refer Here for rest api
• REST APIs use http for communications i.e they have status codes and http methods
• REST API is an architectural style which introduces the concept of
  • Resources: This represents an object (Noun) and they can be accesed using URI (Uniform Resource Identifier)

Library Sample Rest API Design

Designing REST API methods for a library system involves defining the resources (like books, authors, and borrowers) and how clients can interact with them using standard HTTP methods like GET, POST, PUT, and DELETE.

Here’s a basic design for handling common operations in a library using REST API methods:

1. Books Resource

• This will manage the list of books available in the library, including adding, viewing, updating, and deleting books.

Operation	HTTP Method	Endpoint	Description
Get a list of books	GET	/books	Retrieves all books in the library
Get a specific book	GET	/books/{id}	Retrieves a single book by its ID
Add a new book	POST	/books	Adds a new book to the library
Update a book	PUT	/books/{id}	Updates the details of an existing book by its ID
Delete a book	DELETE	/books/{id}	Removes a book from the library by its ID

Example:

• GET /books: Fetch a list of all available books.
• POST /books: Add a new book. The body might contain:
  json
{
"title": "To Kill a Mockingbird",
"author": "Harper Lee",
"isbn": "9780060935467",
"published_date": "1960-07-11"
}

2. Authors Resource

• This will manage the authors of the books.

Operation	HTTP Method	Endpoint	Description
Get a list of authors	GET	/authors	Retrieves all authors in the library
Get a specific author	GET	/authors/{id}	Retrieves a single author by their ID
Add a new author	POST	/authors	Adds a new author to the system
Update an author	PUT	/authors/{id}	Updates the details of an existing author
Delete an author	DELETE	/authors/{id}	Deletes an author by their ID

Example:

• GET /authors: Fetch a list of all authors.
• POST /authors: Add a new author. The body might contain:
  json
{
"name": "Harper Lee",
"dob": "1926-04-28"
}

3. Borrowers Resource

• This will handle library members who borrow books.

Operation	HTTP Method	Endpoint	Description
Get a list of borrowers	GET	/borrowers	Retrieves all borrowers registered in the system
Get a specific borrower	GET	/borrowers/{id}	Retrieves a borrower by their ID
Register a new borrower	POST	/borrowers	Registers a new borrower in the system
Update a borrower’s details	PUT	/borrowers/{id}	Updates the details of an existing borrower
Delete a borrower	DELETE	/borrowers/{id}	Deletes a borrower from the system

Example:

• POST /borrowers: Register a new borrower. The body might contain:
  json
{
"name": "John Doe",
"email": "john.doe@example.com",
"membership_date": "2023-09-10"
}

4. Borrow/Return Books Resource

• This will manage borrowing and returning books by borrowers.

Operation	HTTP Method	Endpoint	Description
Borrow a book	POST	/borrow/{book_id}/borrowers/{id}	Marks a book as borrowed by a specific borrower
Return a book	POST	/return/{book_id}/borrowers/{id}	Marks a book as returned by a borrower
Get borrowed books by user	GET	/borrowers/{id}/borrowed	Retrieves a list of books currently borrowed by the borrower

Example:

• POST /borrow/123/borrowers/456: Borrower with ID 456 borrows the book with ID 123.
• POST /return/123/borrowers/456: The borrower returns the book.

5. Categories or Genres Resource (Optional)

• If you want to manage different categories/genres of books.

Operation	HTTP Method	Endpoint	Description
Get a list of genres	GET	/genres	Retrieves all book genres
Get books by genre	GET	/genres/{id}/books	Retrieves all books in a specific genre
Add a new genre	POST	/genres	Adds a new genre to the system
Delete a genre	DELETE	/genres/{id}	Deletes a genre from the system

Example:

• GET /genres/1/books: Retrieve all books in genre 1 (e.g., Science Fiction).

---

REST API Summary for the Library:

• Books: Add, view, update, and delete books.
• Authors: Add, view, update, and delete authors.
• Borrowers: Register, view, update, and delete library members.
• Borrow/Return: Borrow or return books, track borrowing history.
• Genres: Optionally manage and categorize books by genre.

This basic design gives flexibility to interact with the library system, handle book lending, and manage records, all via simple HTTP requests using REST principles.

Departmental store- REST API Design

Designing a REST API for a departmental store involves handling various resources such as products, categories, customers, orders, and payments. Below is a basic structure for each resource and how you might interact with them using REST API methods.

1. Products Resource

• This resource manages the products available in the store, including viewing, adding, updating, and deleting products.

Operation	HTTP Method	Endpoint	Description
Get a list of products	GET	/products	Retrieves all products in the store
Get a specific product	GET	/products/{id}	Retrieves a single product by its ID
Add a new product	POST	/products	Adds a new product to the store
Update a product	PUT	/products/{id}	Updates an existing product’s details
Delete a product	DELETE	/products/{id}	Removes a product from the store

Example:

• GET /products: Retrieves the list of all products.
• POST /products: Adds a new product. The body might contain:
  json
{
"name": "Laptop",
"category_id": 1,
"price": 800,
"stock": 50
}

2. Categories Resource

• This will manage the categories of products in the store (e.g., electronics, clothing).

Operation	HTTP Method	Endpoint	Description
Get a list of categories	GET	/categories	Retrieves all product categories
Get a specific category	GET	/categories/{id}	Retrieves a single category by its ID
Add a new category	POST	/categories	Adds a new category to the store
Update a category	PUT	/categories/{id}	Updates an existing category
Delete a category	DELETE	/categories/{id}	Removes a category from the store

Example:

• GET /categories: Retrieves the list of all categories.
• POST /categories: Adds a new category. The body might contain:
  json
{
"name": "Electronics"
}

3. Customers Resource

• This resource handles the store’s customers, including creating customer profiles and managing their information.

Operation	HTTP Method	Endpoint	Description
Get a list of customers	GET	/customers	Retrieves all customers
Get a specific customer	GET	/customers/{id}	Retrieves a customer by their ID
Add a new customer	POST	/customers	Registers a new customer
Update customer details	PUT	/customers/{id}	Updates an existing customer’s details
Delete a customer	DELETE	/customers/{id}	Removes a customer from the store

Example:

• POST /customers: Adds a new customer. The body might contain:
  json
{
"name": "John Doe",
"email": "john.doe@example.com",
"address": "123 Main St"
}

4. Orders Resource

• This resource manages customer orders, tracking products that have been purchased, their status, and the customer who placed the order.

Operation	HTTP Method	Endpoint	Description
Get a list of orders	GET	/orders	Retrieves all orders placed by customers
Get a specific order	GET	/orders/{id}	Retrieves details of a specific order
Create a new order	POST	/orders	Places a new order
Update an order status	PUT	/orders/{id}	Updates the status of an order (e.g., shipped, delivered)
Delete an order	DELETE	/orders/{id}	Cancels an order

Example:

• POST /orders: Creates a new order. The body might contain:
  json
{
"customer_id": 123,
"order_items": [
{
"product_id": 1,
"quantity": 2
},
{
"product_id": 3,
"quantity": 1
}
],
"total_price": 500,
"status": "pending"
}

5. Payments Resource

• This resource manages payments for orders, tracking the payment status.

Operation	HTTP Method	Endpoint	Description
Get payment details	GET	/payments/{order_id}	Retrieves the payment status for a specific order
Make a payment	POST	/payments	Makes a payment for an order
Update payment status	PUT	/payments/{id}	Updates the payment status (e.g., paid, refunded)

Example:

• POST /payments: Creates a payment for an order. The body might contain:
  json
{
"order_id": 123,
"payment_method": "credit_card",
"amount": 500,
"status": "paid"
}

6. Cart Resource

• This resource manages customer shopping carts, allowing them to add, view, and remove items before placing an order.

Operation	HTTP Method	Endpoint	Description
View cart items	GET	/cart/{customer_id}	Retrieves all items in a customer’s cart
Add item to cart	POST	/cart/{customer_id}	Adds an item to the customer’s cart
Remove item from cart	DELETE	/cart/{customer_id}/items/{item_id}	Removes an item from the cart

Example:

• POST /cart/123: Adds an item to the cart for customer 123. The body might contain:
  json
{
"product_id": 1,
"quantity": 2
}

7. Inventory Resource

• This resource handles the stock and availability of products in the store.

Operation	HTTP Method	Endpoint	Description
Get current stock for a product	GET	/inventory/{product_id}	Retrieves the stock level for a specific product
Update stock for a product	PUT	/inventory/{product_id}	Updates the stock level for a product

Example:

• PUT /inventory/1: Updates the stock for product 1. The body might contain:
  json
{
"stock": 100
}

---

REST API Summary for Departmental Store:

• Products: Add, view, update, and delete products.
• Categories: Manage product categories.
• Customers: Add, view, update, and delete customer profiles.
• Orders: Create, view, update, and delete orders.
• Payments: Handle payments for orders.
• Cart: Manage the customer’s shopping cart before placing an order.
• Inventory: Track and update the stock of products.

This design provides a flexible and structured way to manage the various operations of a departmental store using REST API methods.

Developing REST APIs in Python

• To develop rest api’s in python we have following frameworks which make it simple
  • Flask
  • Django Restful
  • FastAPI
• Lets use FastAPI to build apis Refer Here
• Fast APIs support asynchronous apis, automatic api documentations
• API Documentations:
  • openapi (Swagger)
  • redoc
• Generally python web applications are hosted on WSGI, but fast api uses asgi using starlette. Fastapis are generally hosted on uvicorn which as asgi
• When we are dealing with rest apis, the values can be passed to server in the following ways
  • url
  • message body
  • query string
  • headers

First fast api application – Calculator

• Create a new folder and add a virtual environment in it
• Refer Here for hello rest api

Library – REST API

• Lets try implementing Books resource

1. Books Resource

• This will manage the list of books available in the library, including adding, viewing, updating, and deleting books.

Operation	HTTP Method	Endpoint	Description
Get a list of books	GET	/books	Retrieves all books in the library
Get a specific book	GET	/books/{id}	Retrieves a single book by its ID
Add a new book	POST	/books	Adds a new book to the library
Update a book	PUT	/books/{id}	Updates the details of an existing book by its ID
Delete a book	DELETE	/books/{id}	Removes a book from the library by its ID

Example:

• GET /books: Fetch a list of all available books.
• POST /books: Add a new book. The body might contain:
  json
{
"title": "To Kill a Mockingbird",
"author": "Harper Lee",
"isbn": "9780060935467",
"published_date": "1960-07-11"
}