Return Data in JSON Format Using FastAPI in Python

FastAPI is a modern, fast, web framework for building APIs with Python 3.7+ based on standard Python type hints. It is designed to be easy to use and efficient, providing automatic generation of OpenAPI and JSON Schema documentation. In this article, we will see how to return data in JSON format using FastAPI in Python.

How to Return Data in Json Format Using Fastapi in Python

Below is the step-by-step procedure by which we can return data in JSON format using FastAPI in Python:

Step 1: Installation

Here, we will install the following libraries and modules before starting.

1. Install Python
2. Install FastAPI
3. Install uvicorn

Step 2: Create a Virtual Environment

In this step, we will create the virtual environment in Python. To create a virtual environment, write the following command in your terminal.

 python3 -m venv venv

Now, activate the virtual environment by using the following command:

venv\Scripts\activate

Now run a command to create and automatically write down dependency in requirements.txt

pip freeze > requirements.txt

Step 3. Write the FastAPI Python Code

In this code, a FastAPI application is created with a single endpoint (“/Hello-world”). When a GET request is made to this endpoint, the Hello function is executed, returning a JSON response containing a nested structure with a “message,” “details,” and information about the author (name and email), along with a list of tags. This demonstrates how FastAPI effortlessly handles JSON serialization, allowing developers to return complex data structures as API responses.

main.py

Python3

from fastapi import FastAPI

app = FastAPI()

@app.get("/Hello-world")
def Hello():
    data = {
        "message": "hello world",
        "details": {
            "author": {
                "name": "Tushar",
                "email": "tushar@example.com"
            },
            "tags": ["fastapi", "python", "web"]

        }
    }
    return data

Step 4: Run the Program

Now run the file using command in terminal.

uvicorn main:app --reload

After that you will something like image below in terminal

Now copy the following command and paste it to the browser to run the following program:

http://127.0.0.1:8000/Hello-world

This is basically says that your server is running at localhost:8000 ,this is the default port at which fastapi server running locally. But it will take you to the home route which we have not defined so it will show this thing.

It is just showing the default error handling you can go to your route and see that it is working. just enter this in tab localhost:8000/Hello-world.

Output:

JSON Data Returned Using FastAPI

Video Demonstration