How to Return JSON Data Using FastAPI?

How to Return Data in JSON Format Using FastAPI

FastAPI is a modern, fast (due to the use of ASGI) web framework for building APIs. It is built on top of Starlette and Pydantic and offers a high level of performance, security, and flexibility.

Returning Data in JSON Format

To return data in JSON format from a FastAPI application, you can use the following steps:

1. Ensure that the data you are returning is JSON-serializable. This means that it can be converted into a string representation that can be parsed by JSON parsers.
2. Use a JSON encoder to convert the data into a JSON string. The json module in Python provides the json.dumps() function, which can be used for this purpose.
3. Return the JSON string as the response from your API endpoint.

Example

Below, you will find a simple example of how to return data in JSON format from a FastAPI application:

from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class User(BaseModel):
    name: str
    age: int

@app.get("/users")
async def get_users():
    users = [
        User(name="John", age=30),
        User(name="Jane", age=25),
    ]
    return users

In this example, the get_users() endpoint returns a list of two User objects. The User object is defined using Pydantic, which ensures that the data is validated before being returned as the response.

Additional Notes

• By default, FastAPI will automatically convert the data returned from your API endpoints into a JSON response. However, if you need to customize the JSON response, you can do so by using the JSONResponse class provided by FastAPI.
• The JSONResponse class allows you to specify the status code of the response, the media type, and the content of the response. You can also use the JSONResponse class to return data that is not JSON-serializable, such as files or binary data

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