Why request bodies carry structured data in FastAPI - See It in Action

Why request bodies carry structured data

📖 Scenario: You are building a simple web API using FastAPI. Your API needs to receive user information like name and age in a structured way so it can process it correctly.

🎯 Goal: Build a FastAPI endpoint that accepts a JSON request body with user data structured as a dictionary with name and age keys.

📋 What You'll Learn

Create a Pydantic model called User with fields name (string) and age (integer).

Create a FastAPI app instance called app.

Create a POST endpoint at /users/ that accepts a User object as the request body.

Return the received user data as JSON in the response.

💡 Why This Matters

🌍 Real World

APIs often receive data from clients in structured formats like JSON. Using models helps keep data organized and validated.

💼 Career

Understanding how to handle structured request bodies is essential for backend developers building reliable web APIs.

1

Create the User data model

Write code to import BaseModel from pydantic and create a class called User that inherits from BaseModel. Add two fields: name of type str and age of type int.

FastAPI

# Your code here to create User model

Need a hint?

Think of User as a form with two fields: name and age. Use BaseModel to define it.

2

Create the FastAPI app instance

Write code to import FastAPI from fastapi and create an instance called app.

FastAPI

from pydantic import BaseModel

class User(BaseModel):
    name: str
    age: int

# Create FastAPI app instance

Need a hint?

FastAPI apps start by creating an app object from the FastAPI class.

3

Create the POST endpoint to receive User data

Write a function called create_user decorated with @app.post("/users/"). The function should accept one parameter called user of type User. The function should return the user object.

FastAPI

from pydantic import BaseModel
from fastapi import FastAPI

class User(BaseModel):
    name: str
    age: int

app = FastAPI()

# Create POST endpoint to receive User data

Need a hint?

Use @app.post("/users/") to create a POST endpoint. The function should accept user: User and return it.

4

Complete the FastAPI app with structured request body

Ensure the full code includes the User model, the app instance, and the create_user POST endpoint that accepts a User object and returns it.

FastAPI

from pydantic import BaseModel
from fastapi import FastAPI

class User(BaseModel):
    name: str
    age: int

app = FastAPI()

@app.post("/users/")
async def create_user(user: User):
    # Return the user object
    return user

Need a hint?

Check that all parts are present: model, app, and endpoint returning the user.