Understanding Client-Server Communication with Flask in Python

Explore the basics of implementing a client-server architecture using Flask in Python. Learn how to set up a server, create APIs, and interact with a client application. The process involves handling API calls, directing requests, and returning data to the client through the server.

• Python
• Flask
• Client-Server
• Web Development
• REST API

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Uploaded on Sep 26, 2024 | 0 Views

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1. Client-Server PYTHON AND FLASK

2. Basic Client - Server Client One Server Many types of clients All connected using a common protocol Browser HTTP(s) Web Server HTTP(s) Mobile App HTTP(s) Desktop Application Client Client

3. Web Servers Industrial Strength: Development: - IIS - Node - Apache - Flask - Nginx - httpd - Litespeed We will use Flask

4. Flask Python module Can host basic commands needed for web application work 1. API Call Flask Web Server Client App REST APIs DB 5. API Return 3. API interacts with DB, gets processes data 2. Web server directs API call to handler Your APIs/ Code 4. API returns data to Web Server

5. Flask basics server side from flask import Flask from flask_restful import Resource, Api from api.hello_world import HelloWorld app = Flask(__name__) #create Flask instance api = Api(app) #api router api.add_resource(HelloWorld, '/hi') #api 'endpoint'

6. Flask basics server side: API from flask import Flask def list_examples(): from flask_restful import Resource, Api return exec_get_all ('SELECT id, foo FROM example_table') from api.hello_world import HelloWorld class HelloWorld(Resource): def get(self): #Handles get request return dict(example.list_examples())

7. Flask basics client side import requests #HTTP library for get/ post ... url = http://locahost:8000/hi') #api 'endpoint' response = requests.get(url, params) #HTTP GET, url=endpoint

8. You now have two applications! First, you will need to start your server (server.py) THEN You will run your unit tests py m unittest v Two commands and TWO terminal windows!!

9. On the wire GET /hi HTTP/1.1 Host: localhost:5000 User-Agent: python-requests/2.22.0 Accept-Encoding: gzip, deflate Accept: */* Connection: keep-alive HTTP/1.0 200 OK Content-Type: application/json Content-Length: 29 Server: Werkzeug/1.0.1 Python/3.8.0 Date: Sat, 26 Sep 2020 16:21:28 GMT { "1": "hello, world!" } The request The response

10. On the wire GET /hi?a=1&b=2 HTTP/1.1 HTTP/1.0 200 OK Content-Type: application/json Content-Length: 29 Server: Werkzeug/1.0.1 Python/3.8.0 Date: Sat, 26 Sep 2020 16:21:28 GMT Host: localhost:5000 User-Agent: python-requests/2.22.0 Accept-Encoding: gzip, deflate Accept: */* Connection: keep-alive { "1": "hello, world!" } The request with params The response