Client-Server Communication with Flask in Python
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Client-Server
PYTHON AND FLASK
Basic Client - Server
Browser
Desktop Application
Mobile App
HTTP(s)
HTTP(s)
HTTP(s)
•
One Server
•
Many types of clients
•
All ‘connected’ using a
common protocol
Web Servers
Industrial Strength:
- IIS
- Apache
- Nginx
- Litespeed
…
Development:
- Node
- Flask
- httpd
…
We will use ‘Flask’
Flask
Python module
Can host basic commands needed
for web application work
•
REST APIs
Client
App
Flask
Web
Server
DB
Your
APIs/
Code
1. API
Call
2. Web server directs API
call to ‘handler’
3. API interacts
with DB, gets
processes data
4. API returns data to
Web Server
5. API
Return
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'
Flask basics – server side: API
from
flask
import
Flask
from
flask_restful
import
Resource, Api
from
api.hello_world
import
HelloWorld
class
HelloWorld
(
Resource
):
def
get
(
self
):
#Handles ‘get’ request
return
dict
(example.list_examples())
def
list_examples
():
return
exec_get_all
(
'SELECT id, foo FROM example_table'
)
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
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!!
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
On the ‘wire’
GET /hi?a=1&b=2 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 – with
params
The response
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.
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Presentation Transcript
Client-Server PYTHON AND FLASK
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
Web Servers Industrial Strength: Development: - IIS - Node - Apache - Flask - Nginx - httpd - Litespeed We will use Flask
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
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'
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())
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
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!!
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
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
