List and set validation in FastAPI - Mini Project: Build & Apply

List and Set Validation with FastAPI

📖 Scenario: You are building a simple FastAPI app that accepts user input for favorite fruits. You want to make sure the input is a list of fruits and also check if the fruits are unique using a set.

🎯 Goal: Create a FastAPI endpoint that accepts a list of fruits, validates it, and converts it to a set to ensure uniqueness.

📋 What You'll Learn

Create a list variable called fruits with exact values: ['apple', 'banana', 'apple', 'orange']

Create a variable called unique_fruits that converts fruits to a set

Create a FastAPI app instance called app

Create a POST endpoint /fruits that accepts a list of strings called fruits in the request body

💡 Why This Matters

🌍 Real World

Validating lists and sets is common when handling user input in web apps, such as filtering unique items or preferences.

💼 Career

Backend developers often use FastAPI to build APIs that validate and process list data efficiently.

1

Create the initial list of fruits

Create a list variable called fruits with these exact values: ['apple', 'banana', 'apple', 'orange']

FastAPI

# Create the list of fruits
# Your code here

Need a hint?

Use square brackets to create a list and include the fruits exactly as shown.

2

Convert the list to a set for uniqueness

Create a variable called unique_fruits that converts the list fruits to a set using set(fruits)

FastAPI

fruits = ['apple', 'banana', 'apple', 'orange']
# Convert fruits list to a set called unique_fruits
# Your code here

Need a hint?

Use the set() function to remove duplicates from the list.

3

Create a FastAPI app instance

Import FastAPI from fastapi and create an app instance called app using app = FastAPI()

FastAPI

fruits = ['apple', 'banana', 'apple', 'orange']
unique_fruits = set(fruits)
# Import FastAPI and create app instance
# Your code here

Need a hint?

Use from fastapi import FastAPI and then create app = FastAPI().

4

Create a POST endpoint to accept a list of fruits

Create a POST endpoint /fruits using @app.post('/fruits') that accepts a parameter fruits of type list[str] in the request body and returns the set of unique fruits using set(fruits)

FastAPI

from fastapi import FastAPI

fruits = ['apple', 'banana', 'apple', 'orange']
unique_fruits = set(fruits)

app = FastAPI()

# Create POST endpoint /fruits that accepts list[str] fruits and returns set of unique fruits
# Your code here

Need a hint?

Use @app.post('/fruits') decorator and define an async function with parameter fruits: List[str]. Return the unique fruits as a list inside a dictionary.