CS504070 - Homework 8: Request Body - List Fields and Nested Models

cs504070-homework-8.md

CS504070 - Homework 8

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Exercise 1: Basic Request Body with List Field

Task:

1. Create a FastAPI application.
2. Define a Pydantic model called Item with two fields: name (string) and price (float).
3. Define another model Cart, which includes a list of Item instances.
4. Create a POST endpoint /cart that accepts a Cart request body and returns it as a response.

Example Input (JSON):

{
  "items": [
    {"name": "Laptop", "price": 1200.50},
    {"name": "Mouse", "price": 25.99}
  ]
}

Expected Output (JSON):

{
  "items": [
    {"name": "Laptop", "price": 1200.50},
    {"name": "Mouse", "price": 25.99}
  ]
}

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Exercise 2: Validations for List and Nested Models

Task:

1. Extend Item to add:
   • price must be greater than 0.
   • name must be at least 3 characters long.
2. In Cart, ensure that the items list contains at least one Item.
3. Return a 400 Bad Request error if any validation fails.

Example Invalid Input (JSON):

{
  "items": [
    {"name": "PC", "price": -500}
  ]
}

Expected Response (400 Bad Request):

{
  "detail": [
    {
      "loc": ["body", "items", 0, "price"],
      "msg": "Price must be greater than 0",
      "type": "value_error"
    }
  ]
}

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Exercise 3: Nested Models with User Information

Task:

1. Create a new model User, with fields:
   • username (string, min 3 chars)
   • email (valid email format)
2. Modify Cart to include a user field of type User.
3. Update the /cart endpoint to return both the user and items.

Example Input (JSON):

{
  "user": {
    "username": "john_doe",
    "email": "[email protected]"
  },
  "items": [
    {"name": "Keyboard", "price": 45.00},
    {"name": "Monitor", "price": 250.00}
  ]
}

Expected Output (JSON):

{
  "user": {
    "username": "john_doe",
    "email": "[email protected]"
  },
  "items": [
    {"name": "Keyboard", "price": 45.00},
    {"name": "Monitor", "price": 250.00}
  ]
}

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Exercise 4: Calculate Total Price and Apply Discounts

Task:

1. Extend the /cart endpoint to calculate the total price of items.
2. If the total price is greater than $500, apply a 10% discount.
3. Return the total_price (after discount, if applicable) in the response.

Example Input (JSON):

{
  "user": {
    "username": "jane_doe",
    "email": "[email protected]"
  },
  "items": [
    {"name": "Gaming Laptop", "price": 1200.00},
    {"name": "Headset", "price": 50.00}
  ]
}

Expected Output (JSON):

{
  "user": {
    "username": "jane_doe",
    "email": "[email protected]"
  },
  "items": [
    {"name": "Gaming Laptop", "price": 1200.00},
    {"name": "Headset", "price": 50.00}
  ],
  "total_price": 1125.00
}

(A 10% discount is applied to the total price of $1250, reducing it to $1125.)