Create REST API using FastAPI in Python

This tutorial will guide you in creating REST APIs from scratch using FastAPI in Python.

FastAPI is a modern Python web framework for building fast, high-performance APIs.

FastAPI is fast because it uses ASGI. ASGI stands for Asynchronous Server Gateway Interface. ASGI is a successor to the WSGI. WSGI stands for Web Server Gateway Interface. WSGI is synchronous and therefore is slower than ASGI. Frameworks like Django, Flask, Falcon use WSGI.

Follow the steps below to complete this tutorial:

STEP 1 - Setting Up Environment

  1. Before you start, make sure you have Python, pip and virtual environment installed on your system. You can check your Python version by running python --version in your terminal.
  2. Create a new project folder, and then navigate to that folder via a terminal or command prompt:
    3. mkdir example-app

cd example-app

  3. Next, inside the folder, create a virtual environment using the command given below:

    4. Windows:

    py -m venv env

    Unix/macOS:

    python3 -m venv env

  4. Activate the virtual environment using the following command:

    5. Windows:

    .\env\Scripts\activate

    Unix/macOS:

    source env/bin/activate

STEP 2 - Installing Dependencies

  1. Install FastAPI dependency:
    2. pip install fastapi

  2. Install uvicorn. Uvicorn is an implementation of ASGI server for fast performance. To install uvicorn, use this command:
    3. pip install "uvicorn[standard]"

STEP 3 - Create FastAPI Endpoints

Create a Python file (for example: main.py) inside the project folder to define your FastAPI application. Import FastAPI and create an instance of it. Next, you can define your API endpoints. Create Python functions that correspond to the HTTP methods you want to support (e.g., GET, POST, PUT, DELETE). Use FastAPI decorators to define routes and request parameters:

import uvicorn
from typing import Optional
from fastapi import FastAPI
from pydantic import BaseModel, Field

app = FastAPI()

class User(BaseModel):
    user_id: Optional[int] = None
    first_name: str
    last_name: str
    email: str
    father_name: Optional[str] = Field(
        None, title="The father name of the user", max_length=300
    )
    age: float = Field(..., gt=0,
                       description="The age must be greater than zero")


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/users/{user_id}")
def read_user(user_id: int):
    return {"user_id": user_id, "full_name": "Danny Manny", "email": "danny.manny@gmail.com"}


@app.post("/users/add")
def add_user(user: User):
    return {"full_name": user.first_name+" "+user.last_name}


@app.put("/users/update")
def update_user(user: User):
    return {"user_id": user.user_id, "full_name": user.first_name+" "+user.last_name, "email": user.email}


@app.delete("/users/{user_id}/delete")
def delete_user(user_id: int):
    return {"user_id": user_id, "is_deleted": True}


if __name__ == '__main__':
    uvicorn.run(app, host='127.0.0.1', port=8005)
    print("running")

STEP 4 - Run and Test your FastAPI Application

When you run your application, make sure your virtual environment is activated. Execute your Python file (main.py):

python main.py

Once your application starts, you can see tha documentation of your APIs at http://127.0.0.1:8005/docs.