An Introduction to Python FastAPI & Swagger UI

Aysel Aydin
3 min readJan 7, 2023

In this Python tutorial, you will learn about FastAPI that a Web framework for developing RESTful APIs in Python.

FastAPI is a modern API framework in Python.

  • Very easy to learn the framework and develop the code
  • Easy to convert the code from Flask to FastAPI
  • The framework is production ready and it is widely used in industry.
  • Faster performance compared to other frameworks
  • Works on the Python version greater than 3.6
  • API documents will get generated automatically without any extra lines of code and additional effort.


To develop and run a fastapi application, you need to install 2 packages.

  • The first package is the fastapi package
pip install fastapi
  • The second one is the ASGI server for deploying the application in production.
pip install uvicorn

Create a First API

from fastapi import FastAPI

app = FastAPI()

async def my_first_get_api():
return {"message":"First FastAPI example"}

After writing the code, now you need a server program to run it. You should run the code below in the terminal.

python -m uvicorn main:app --reload

After successfully running the code, the app will run on port 8000. Open the URL in your web browser. You should see a screen like the image below.

Now let's check the API documentation of this application. Type the URL This will open up the Swagger UI

Expand the “My First Get Api

Click the “Try it out” button in the upper right corner. The Execute button appears on the screen.

In the next tutorial, I will be covering fastapi in more detail like the image below. Follow me for learning Python, Machine Learning, Deep Learning and Data Science to get extra knowledge.

Check out my Github repository for more example👇👇👇