Flask restful API

19 Jan 2023

A restful API is a starndard interface through which application services can be accessed. After building an application that offer some services, it can be wrapped in an api and deploy on some server where the wervices can be remotely accessed. In this, I briefly go through the steps required to develop restful API using flask. The steps can be summarized as follows:

Load the required libraries

 from flask import Flask, requests
 from flask_restful import Resource, Api

Instantiate flask app and wrap it in an API
```
 app = Flask(__name__)
 api = Api(app)
```

create the Resource

 class HelloWorld(Resource):
     def get(self):
       return "Hello World!"

     def post(self):
       json_data = request.get_json(force=True)

add resource to the wrapped app
```
 api.add_resource(HelloWorld,'/key')
```

set up the app to run as main

 if __name__ = "__main__":
   app.run(debug==true)

Having served up the website, it is time for the user to ping the api.

There are many ways to do this:

    curl -H "Content-Type : application/json" -H "Accept : application/json" -X POST
    --data "{"recipes" :{"101":"Abe"}}" http://localhost:5000/rec

The first header above -H tells Flask that we are expecting a JSON input so we can easily use flask.request() to extract our data which is specified with --d
The second header tells flask that we are also expecting it to serve our query in json.
-X POST is a bit redundant as it tells flask that this is a POST request.

Alternatively, the first header can be removed as below in which case we get an error. This is because flask does not know what the content type is. However, to tell flask to parse the data as JSON nevertheless, we use flask.request.get_json(force=True)

    curl -H "Accept : application/json" -X POST
    --data "{"recipes" :{"101":"Abe"}}" http://localhost:5000/rec

Finally, we can still remove the final header by jsonifying the returned value. bash curl -X POST --data "{"recipes" :{"101":"Abe"}}" http://localhost:5000/rec

JSON

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Flask restful API