Basic query parameter declaration in FastAPI - Mini Project: Build & Apply

Basic query parameter declaration

📖 Scenario: You are building a simple web API using FastAPI. Your API will greet users by their name, which will be provided as a query parameter in the URL.

🎯 Goal: Create a FastAPI app that accepts a query parameter called name and returns a greeting message including that name.

📋 What You'll Learn

Create a FastAPI app instance named app

Define a GET endpoint at path /greet

Declare a query parameter named name of type str in the endpoint function

Return a dictionary with a key message and value "Hello, {name}!" where {name} is the query parameter value

💡 Why This Matters

🌍 Real World

APIs often need to accept user input via query parameters to customize responses, such as filtering data or personalizing messages.

💼 Career

Understanding how to declare and use query parameters in FastAPI is essential for backend developers building web APIs.

1

Create FastAPI app instance

Import FastAPI from fastapi and create an app instance called app.

FastAPI

from fastapi import FastAPI

# Create FastAPI app instance called app
# Your code here

Need a hint?

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

2

Define GET endpoint at /greet

Add a GET endpoint to app with the path /greet using the @app.get("/greet") decorator. Define a function called greet with no parameters yet.

FastAPI

from fastapi import FastAPI

app = FastAPI()

# Define GET endpoint at /greet
@app.get("/greet")
def greet():
    pass  # Your code here

Need a hint?

Use @app.get("/greet") above the function greet.

3

Add query parameter name

Modify the greet function to accept a query parameter called name of type str.

FastAPI

from fastapi import FastAPI

app = FastAPI()

@app.get("/greet")
def greet(name: str):
    # Your code here

Need a hint?

Add name: str inside the parentheses of the greet function.

4

Return greeting message

Return a dictionary with key message and value "Hello, {name}!" using an f-string inside the greet function.

FastAPI

from fastapi import FastAPI

app = FastAPI()

@app.get("/greet")
def greet(name: str):
    # Return greeting message
    # Your code here

Need a hint?

Use return {"message": f"Hello, {name}!"} to send the greeting.