Multiple response types in FastAPI - Mini Project: Build & Apply

Multiple Response Types with FastAPI

📖 Scenario: You are building a simple web API that can return different types of responses depending on the request. Sometimes it returns plain text, sometimes JSON data.

🎯 Goal: Create a FastAPI app with one endpoint /response that returns either plain text or JSON depending on a query parameter.

📋 What You'll Learn

Create a FastAPI app instance called app

Add a GET endpoint /response with a query parameter type

If type is text, return plain text response

If type is json, return JSON response with a dictionary

Use correct FastAPI response types for each case

💡 Why This Matters

🌍 Real World

APIs often need to return different formats like JSON or plain text depending on client needs.

💼 Career

Knowing how to handle multiple response types is important for backend developers building flexible APIs.

1

Create FastAPI app instance

Create a FastAPI app instance called app by importing FastAPI and initializing it.

FastAPI

from fastapi import FastAPI

# Create FastAPI app instance called app
# Your code here

Need a hint?

Use FastAPI() to create the app instance and assign it to app.

2

Add GET endpoint with query parameter

Add a GET endpoint /response to the app that accepts a query parameter called type of type str.

FastAPI

from fastapi import FastAPI

app = FastAPI()

# Add GET endpoint /response with query parameter type: str
# Your code here

Need a hint?

Use @app.get("/response") decorator and define an async function with type: str parameter.

3

Return plain text or JSON based on query parameter

Inside the get_response function, return plain text 'This is plain text' if type equals 'text'. Otherwise, return a JSON dictionary {"message": "This is JSON"}.

FastAPI

from fastapi import FastAPI

app = FastAPI()

@app.get("/response")
async def get_response(type: str):
    # Return plain text if type is 'text', else return JSON
    # Your code here

Need a hint?

Use an if statement to check type and return the correct response.

4

Use correct response classes for text and JSON

Import PlainTextResponse from fastapi.responses and update the get_response function to return PlainTextResponse with the text when type is 'text'. Return the JSON dictionary directly otherwise.

FastAPI

from fastapi import FastAPI
from fastapi.responses import PlainTextResponse

app = FastAPI()

@app.get("/response")
async def get_response(type: str):
    # Return PlainTextResponse for text type
    # Your code here

Need a hint?

Use PlainTextResponse to send plain text responses properly in FastAPI.