Lab1 Build Your First Joke API

Introduction

FastAPI is one of the fastest-growing Python frameworks for building APIs. It is super fast, easy to learn, and perfect for beginners.

In this tutorial, you’ll build your first FastAPI application — a simple API that returns a random joke using the pyjokes library.

This guide is written for absolute beginners, so no prior backend experience is required.

Understanding the Requirements

Before writing any code, let’s understand what tools we’ll use:

What you need:

Python 3 installed
Basic understanding of functions and imports
A terminal or command prompt
Two simple Python libraries:
- fastapi
- uvicorn
- pyjokes

The application we build will:

Start a FastAPI server
Provide an endpoint /joke
Return a random joke in JSON format when visited

Setting Up Your Environment

Open your terminal and install the required libraries:

pip install fastapi uvicorn pyjokes

To confirm installation:

      
       python -m pip show fastapi
python -m pip show uvicorn
python -m pip show pyjokes

Everything should show a valid version number.

Creating Your FastAPI App

Create a new file called main.py and add the following code:

      
       from fastapi import FastAPI
import pyjokes

app = FastAPI()

@app.get("/joke")
def tell_joke():
    print(joke := pyjokes.get_joke())
    return {"joke": joke}

Code Explanation

1. Importing Modules

      
       from fastapi import FastAPI
import pyjokes

FastAPI lets you create API endpoints easily.
pyjokes gives us ready-made programming jokes.

2. Creating an App Instance

      
       app = FastAPI()

This creates your FastAPI application. Think of it as the “brain” of your API.

3. Creating an Endpoint

      
       @app.get("/joke")
def tell_joke():

@app.get("/joke") tells FastAPI:
“When someone visits /joke, run the function below.”

4. Returning a Joke

      
       return {"joke": joke}

FastAPI automatically converts this Python dict into JSON.

Running the FastAPI App

Use the following command in the folder where main.py is saved:

python -m uvicorn main:app --reload

What this means:

uvicorn → server that runs FastAPI
main → the filename main.py
app → the FastAPI instance inside that file
--reload → restart automatically whenever you edit the file

Testing Your API

Once the server is running, open your browser and visit:

http://127.0.0.1:8000/joke

You should see something like:

      
       {
  "joke": "Why do programmers prefer dark mode? Because light attracts bugs!"
}

Bonus: Automatic Documentation!

FastAPI automatically generates documentation pages.

Open these:

Swagger UI

http://127.0.0.1:8000/docs

ReDoc

http://127.0.0.1:8000/redoc

1763597234731

You get beautiful, interactive API docs for free.

Complete Source Code

      
       # pip install fastapi uvicorn pyjokes

from fastapi import FastAPI
import pyjokes

app = FastAPI()

@app.get("/joke")
def tell_joke():
    print(joke := pyjokes.get_joke())
    return {"joke": joke}

# Run using:
# python -m uvicorn main:app --reload

Conclusion

You have now built your first FastAPI project!

You learned:

How to install FastAPI
How to create an API endpoint
How to return JSON responses
How to run a development server
How to access auto-generated API docs

This is only the beginning — FastAPI can handle authentication, databases, async tasks, and much more.

Happy coding!

Website: https://www.pyshine.com Author: PyShine