Get started with Fast API ⚡🚀

Hello, everyone

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In this blog, we will know how to get started with Fast API ⚡

But what is Fast API 🤔 ?

FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.6+ based on standard Python type hints.

So let's get started with the tutorial with wasting any time 🏃‍♂️ 🚀

Installing the dependencies

You would require the follwing dependencies to follow along with the tutorial

Fast API
Uvicorn (to start a local development server)

Let's install the above dependencies using the following command

pip install fastapi uvicorn

Creating a basic API

Now let's create a desired for your Fast API project and cd into that directory

mkdir fast-api-demo-project
cd fast-api-demo-project

Let's now create a main.py file

touch main.py

Open the directory in your favourite code editor, I will be using VScode for this tutorial

Importing Fast API into main.py

As we have installed the required dependencies, let's import them into our main.py file, so that we can use them 🎉

from fastapi import FastAPI
app = FastAPI()

Creating a basic API which returns Hello, World!

Now let's let's return the message Hello, World, when we visit the root directory of our Fast API

The root directory is /

@app.get('/')
async def helloworld():
    return {"message": "Hello, World"}

Running the Fast API app locally using Uvicorn

Now we have programmed the application to return Hello, World when we visit the root directory. But the code doesn't run by itself 😱. To run it, we would need a server, in this case uvicorn would be our server via which we would run our Fast API application.

To run the Fast API application using the following command

uvicorn main:app --reload

Let's break the command down into pieces and understand each piece importance:

main: This refers to the filename
app: This refers to the object of FastAPI which we have created in the main.py file
--reload: This will restart the server automatically, whenever there are changes in the file

This will start the Fast API at port 8000. Visit localhost:8000, to view your Fast API application in action 🤩.

Path parameters

Path parameters help scope the API call down to a single resource. These parameters are enclosed in curly brackets {}, and they offer a way for you to control the representation of specific resources.

Let's view them in action

@app.get("/item/{item_id}")
def read_item_id(item_id):
  return f"The item ID is {item_id}"

The result would look like this :

Query parameters

Query parameters are optional. In FastAPI, function parameters that aren’t declared as part of the path parameters are automatically interpreted as query parameters.

Let's view them in action

languages = [
                {
                    "name": "Python",
                    "id" : "0"
                },
                {
                    "name" : "HTML", 
                    "id" : "1"
                },
                {
                    "name" : "CSS",
                    "id" : "2"
                },
                {
                    "name" : "JavaScript",
                    "id" : "3"
                }
            ]

Here I have created a list with the the names of languages which I know

@app.get("/languages")
async def read_languages(id: Optional[str] = None):
    if id:
        return languages[int(id)]
    return languages

This would return the languages list if a query isn't specified, else it would return the element of that index from the list

🤔 But how to declare queries ??

To use queries, we will be using ? symbol specified with the query name and the query value

For example:

/languages?id=2, would return the element with the of index 2 from the languages list

👋 That's it for this blog, hope you have learned something useful from this blog. Meet you the next week with some other interesting blog 🥳

Kira