REST API

Largely based on this Udemy course

What is a web server?

Sometimes referred to the hardware
Sometimes referred to a piece of software designed to respond to a user request

What is a request?

A request is data that a user/web app sends to a web server

GET /HTTP/1.1
Host www.google.com

What are some ways in which a server might respond to a request?

Error
HTML code
Some processed output
Nothing

In what cases might a web server throw an error?

If it does not support HTTP (eg: an SMTP server)
If path not found (404)
If server is unavailable

Give an example of what a request looks like when you request a web page

When you access https://twitter.com/login

GET /login HTTP/1.1
Host: https://twitter.com

What are the different HTTP verbs and their meanings?

Verb	Meaning	Example
GET	(User) Retrieve something	GET /login
POST	(Server) Receive data and use it	POST /item {'name':'chair','price':9.99}
PUT	Makes sure that there is something. If there isn't anything it will create	PUT /item {'name':'chair','price':9.99}
DELETE	Remove something	DELETE /item/1

What is REST?

Its a way of thinking/designing how a web server responds to a user's requests
Two main characteristics:
- Web server doesn't respond with data, responds with resources instead
- Interactions are stateless

What are resources in REST?

Resources are basically abstractions that encapsulate data. Its a way of thinking about data and how the server and user use it for interaction. GET /item/chair is retrieving the chair resource

Give an example to explain what is meant by stateless in REST?

A user logs into web application
Server does not keep track of requests and responses related to the login and thus does not know that the user is logged in
The web application must send enough data to identify the user in every request or else the server won't associate the request with the user
In the same way, the server must be programmed to associate every request to the specific user

Flask Coding Conventions, Tips & Tricks

POST Request

from flask import Flask

app = Flask(__name__)

@app.route('/store',methods=['POST'])
def some_function():
	pass

GET Request

from flask import Flask

app = Flask(__name__)

@app.route('/store') #default is GET
def some_function():
	pass

POST Request with argument

from flask import Flask

app = Flask(__name__)

@app.route('/store/<string: name>/item',methods=['POST'])
def some_function(name):
	pass

Returning data using JSONify

jsonify is required to convert Python dictionary into a json object that can be read by JavaScript

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/store/<string: name>/item',methods=['POST'])
def some_function(name):
	some_python_dicitonary = {....}
	return jsonify(some_python_dicitonary)

Receiving input data using Request

from flask import Flask, jsonify, request

app = Flask(__name__)

old_data =[{...},{...},{...}]
@app.route('/store/<string: name>/item',methods=['POST'])
def some_function(name):
	request_data = request.get_json() #converts json to dictionary
	new_data = {
				'key1':request_data['key1']
				'key2':request_data['key2']
				}
	old_data.ppend(new_data)
	return jsonify(new_data)

aishwaryaprabhat/Flask