Pydantic model basics in FastAPI - Mini Project: Build & Apply

Pydantic model basics

📖 Scenario: You are building a simple FastAPI app to manage user data. You want to use Pydantic models to define the shape of the user data clearly and safely.

🎯 Goal: Create a Pydantic model called User with specific fields, then use it in a FastAPI endpoint to accept user data.

📋 What You'll Learn

Create a Pydantic model named User with fields id (int), name (str), and email (str).

Add a variable app as a FastAPI instance.

Create a POST endpoint /users/ that accepts a User model as input.

Return the received User data as JSON in the response.

💡 Why This Matters

🌍 Real World

Using Pydantic models in FastAPI helps create APIs that clearly define what data they expect and return. This reduces bugs and improves communication between frontend and backend.

💼 Career

Many backend developer jobs require knowledge of FastAPI and Pydantic for building modern, fast, and reliable APIs.

1

Create the Pydantic model

Create a Pydantic model called User with these exact fields and types: id as int, name as str, and email as str. Import BaseModel from pydantic.

FastAPI

from pydantic import BaseModel

# Define the User model here
# Your code here

Need a hint?

Remember to import BaseModel from pydantic and create a class User that inherits from it.

2

Create the FastAPI app instance

Import FastAPI from fastapi and create a variable called app that is an instance of FastAPI().

FastAPI

from pydantic import BaseModel
from fastapi import FastAPI

class User(BaseModel):
    id: int
    name: str
    email: str

# Create FastAPI app instance
# Your code here

Need a hint?

Use app = FastAPI() to create the app instance.

3

Create the POST endpoint to accept User data

Create a POST endpoint at path /users/ using the @app.post decorator. Define a function called create_user that takes a parameter user of type User. The function should return the user object.

FastAPI

from pydantic import BaseModel
from fastapi import FastAPI

class User(BaseModel):
    id: int
    name: str
    email: str

app = FastAPI()

# Create POST endpoint /users/
# Your code here

Need a hint?

Use @app.post('/users/') and define a function with parameter user: User that returns user.

4

Complete the FastAPI app with Pydantic model usage

Ensure the full code includes the import statements, the User model, the app instance, and the POST endpoint /users/ that accepts and returns a User object.

FastAPI

from pydantic import BaseModel
from fastapi import FastAPI

class User(BaseModel):
    id: int
    name: str
    email: str

app = FastAPI()

@app.post('/users/')
def create_user(user: User):
    return user

# Finalize the app code
# Your code here

Need a hint?

Check that all parts are included: imports, model, app instance, and endpoint.