Flask Pyth thon on web eb fram amewor orks ks Django Roughly - PowerPoint PPT Presentation

Flask

Pyth thon on web eb fram amewor orks ks  Django  Roughly follows MVC pattern  Steeper learning curve.  Flask  Initially an April Fools joke  “Micro” -framework: minimal approach.  Smaller learning curve  http://flask.pocoo.org/docs/0.12/quickstart/#a-minimal-application  Scaffolded video tutorial  https://www.youtube.com/watch?v=iSrZ6r7hwdM&list=PL0DA14EB3618A350 7 Portland State University CS 430P/530 Internet, Web & Cloud Systems

Fl Flas ask k direct rector ory y st struct ucture ure  ./ app.py  Entry-point for program static/  Directory holding static content (e.g. images, regular HTML) templates/  Directory holding Jinja2 HTML templates Portland State University CS 430P/530 Internet, Web & Cloud Systems

Hello ello world ld  app.py  Create app as a Flask object  Use route() method of Flask with parameter '/' to wrap a function that will return a page when the URL is accessed  When called directly by python , use the run() method of Flask to launch the web app on all IP addresses of the host using port 8888  Not run when integrated with apache2/nginx, wsgi Portland State University CS 430P/530 Internet, Web & Cloud Systems

% virtualenv – p python3 env % source env/bin/activate % pip install flask % python app.py * Serving Flask app "foo" (lazy loading) * Environment: production WARNING: Do not use the development server in a production environment. Use a production WSGI server instead. * Debug mode: off * Running on http://0.0.0.0:8888/ (Press CTRL+C to quit) Portland State University CS 430P/530 Internet, Web & Cloud Systems

Gu Gues estbo tbook ok app pplica licatio tion n (v1) . ├── Model.py ├── model_pylist.py  https://bitbucket.org/wuchangfeng/cs430-src ├── app.py ├── requirements.txt  WebDev_Guestbook_v1_pylist ├── templates  Simple MVC app in Python/Flask │ ├── layout.html │ └── index.html  Models └── static  Base class Model to define interface in Model.py └── style.css  Important to implement additional models  Python lists model in model_pylist.py  Stub for SQLite model in model_sqlite3.py  Controller and entrypoint in app.py  View in Jinja2 templates  Base HTML in templates/layout.html  Derived single page templates/index.html  Python package requirements for pip  requirements.txt Portland State University CS 430P/530 Internet, Web & Cloud Systems

Model del (base se) ) in Model.py . ├── Model.py ├── model_pylist.py  Base class for model ├── app.py ├── requirements.txt  Defines interface derived models must adhere to ├── templates  Two functions │ ├── layout.html │ └── index.html  select() to return list containing all entries └── static  insert() to insert new entry └── style.css class Model (): def select( self ): """ Gets all entries from the database :return: List of lists containing all rows of database """ pass def insert( self , name, email, message): """ Inserts entry into database :param name: String :param email: String :param message: String :return: True :raises: Database errors on connection and insertion """ pass Portland State University CS 430P/530 Internet, Web & Cloud Systems

model_pylist.py . ├── Model.py ├── model_pylist.py  Derived class that implements Model using ├── app.py ├── requirements.txt Python lists ├── templates  Does not persist when server restarts │ ├── layout.html │ └── index.html  Not appropriate for multi-threaded servers or cloud └── static deployments └── style.css class model (Model): """ Initializes null list """ def __init__( self ): self .guestentries = [] """ Return current list """ def select( self ): return self .guestentries """ Append list containing name, e-mail, date, and message to guestentries list """ def insert( self , name, email, message): params = [name, email, date.today(), message] self .guestentries.append(params) return True Portland State University CS 430P/530 Internet, Web & Cloud Systems

Contr troller oller in app.py . ├── Model.py ├── model_pylist.py  Import functions from flask, set model ├── app.py  Create app and model ├── requirements.txt ├── templates  Register route to implement main page │ ├── layout.html  Define function to get all entries from model via select() │ └── index.html  Uses a list comprehension to create a list of dictionaries with all entries └── static  Pass dictionary to index.html Jinja2 template via └── style.css render_template to return rendered page from flask import Flask, redirect, request, url_for, render_template # from model_sqlite3 import model from model_pylist import model # Set model app = Flask(__name__) # Create Flask app model = model() @app .route('/') # Function decorator ==> app.route('/',index()) @app .route('/index.html') def index(): # Generate list of dicts containing entries entries = [dict(name=row[0], email=row[1], signed_on=row[2], message=row[3] ) for row in model.select()] return render_template('index.html', entries=entries) Portland State University CS 430P/530 Internet, Web & Cloud Systems

 Register route to implement POST handling of . sign URL in HTML form submission (will see ├── Model.py ├── model_pylist.py this later) ├── app.py  Insert entry via model's insert() method ├── requirements.txt ├── templates  Use Flask's request.form to get form │ ├── layout.html submission values by name │ └── index.html └── static  Note: model class will insert signed_on date └── style.css  Redirect user back to main page  Note: sign route does not have GET method @app .route('/sign', methods=['POST']) def sign(): model.insert(request.form['name'], request.form['email'], request.form['message']) return redirect(url_for('index')) Portland State University CS 430P/530 Internet, Web & Cloud Systems

View w via Ji Jinja nja2 2 tem empla plates es . ├── Model.py ├── model_pylist.py  Base page is like a base class ├── app.py ├── requirements.txt  Sub pages are like derived classes ├── templates  App base page layout.html │ ├── layout.html │ └── index.html  Contains empty content block └── static └── style.css <!doctype html> <html> <title> My Visitors </title> <link rel=stylesheet type=text/css href="{{ url_for('static', filename='style.css') }}" > <div class=page > {% block content %} {% endblock %} </div> ... ... </html> Portland State University CS 430P/530 Internet, Web & Cloud Systems

.  Derived page index.html that fills in ├── Model.py content block ├── model_pylist.py ├── app.py  Sequence through entries list of dictionaries ├── requirements.txt containing guestbook data ├── templates │ ├── layout.html │ └── index.html {% extends "layout.html" %} └── static {% block content %} └── style.css < h2 >Guestbook</ h2 > < form action="{{ url_for('sign') }}" method=post> < p class="heading">Name: < input type=text name=name></ p > < p class="heading">Email: < input type=text name=email></ p > < p class="heading">Message: < textarea rows=5 cols=50 name=message></ textarea ></ p > < p >< input type=submit value=Sign></ p > </ form > < h2 >Entries</ h2 > {% for entry in entries %} < p class=entry> {{ entry.name }} &lt; {{ entry.email }} &gt; < br > signed on {{ entry.signed_on }}< br > {{ entry.message }} </ p > {% endfor %} {% endblock %} Portland State University CS 430P/530 Internet, Web & Cloud Systems

Gu Gues estbo tbook ok app pp v2 ├── app.py ├── gbmodel │ ├── __init__.py │ ├── Model.py │ ├── model_pylist.py │ └── model_sqlite3.py ├── index.py ├── sign.py └── templates ├── index.html └── sign.html  https://bitbucket.org/wuchangfeng/cs430-src  WebDev_Guestbook_v2_modules_mvp  Modularize code via Python packages  Create package for models named gbmodel  Directory name used as package name (e.g. import gbmodel within app.py )  __init__.py executed upon import  Organize into Model-View-Presenter pattern with Flask views  Index presenter for viewing guestbook ( index.py , index.html )  Sign presenter for inserting new entry ( sign.py , sign.html ) Portland State University CS 430P/530 Internet, Web & Cloud Systems