Flask – Python

Max Claus Nunes
maxcnunes@gmail.com
http://blog.maxcnunes.com
https://github.com/maxcnunes/flask_bravi

FLASK IS
• Flask is a micro-framework for Python
• Easy to code
• Easy to configure
• Flask won’t make many decisions for
you, such as what database to use.
• Has an excellent documentation
• RESTful
• Testable

FLASK IS
BASED ON WERKZEUG AND JINJA 2

WSGI Template Engine

FLASK IS
EXTENSIBLE AND KEEPS THE CORE SIMPLE

• Flask-Admin • Flask-Restless
• Flask-Cache • Flask-
• Flask-OpendID SQLAlchemy
• Flask-Mail • Flask-Testing
• Flask- • Flask-WTF
MongoAlchemy • Flask-Uploads

VIRTUALENV
Installing

pip install virtualenv

Configuring

cd ~/YOUR_MAIN_FOLDER
mkdir virtualenvs
cd virtualenvs
virtualenv NAME_YOUR_ENV --no-site-packages

Activating Deactivating

source NAME_YOUR_ENV/bin/activate deactivate

FLASK – THE FIRST APP
Installing pip install Flask

Coding # Import Flask library
from flask import Flask

# Initialize the app from Flask
app = Flask(__name__)

hello.py
# Define a route to hello_world function
@app.route('/')
def hello_world():
return 'Hello World!'

# Run the app on http://localhost:8085
app.run(debug=True,port=8085)

Running python hello.py

6 LINES OF CODE AND
THIS WORKS

SQLALCHEMY
Installing pip install Flask-Sqlalchemy

Coding the Model
from braviapp import db

bravibraviappmodels.py
class News(db.Model):
# Define the properties mapped to database columns
id = db.Column(db.Integer, primary_key = True)
title = db.Column(db.String(100), nullable = False)
text = db.Column(db.Text, nullable = False)

def __init__(self, title, text):
self.title = title
self.text = text

def __repr__(self):
return '<News %r>' % self.title

WTFORMS
Installing pip install Flask-WTF

Coding the Form

bravibraviappmodels.py
# third party imports
from flask.ext.wtf import Form, TextField, TextAreaField,
Required

class NewsCreateForm(Form):
title = TextField('Title', [Required()])
text = TextAreaField('Text', [Required()])

TEMPLATES – BASE HTML
<!DOCTYPE html>
<html>
<head>
<title>{% block title %}Flask - Bravi{% endblock %}</title>
<link rel="stylesheet" href="/static/css/main.css" />
{% block css %}{% endblock %}
{% block script %}{% endblock %}
</head>
<body>

bravitemplatesbase.html
<div id="wrapper{{ wrapper_type }}">
<div id="header">
{% block header %}
<h1><a id="link-title-home"
href="{{ url_for('all') }}">Bravi News</a></h1>
{% endblock %}
</div>
<div id="messages">
{% for category, msg in get_flashed_messages(with_categories=true) %}
<p class="messages flash-{{ category }}">{{ msg }}</p>
{% endfor %}
</div>
<div id="content" class="shadow">
{% block content %}{% endblock %}
</div>
<div id="footer">{% block footer %}{% endblock %}</div>
</div>
</body>
</html>

TEMPLATES – LIST
{% extends "base.html" %}

{% block content %}
<h2>All News</h2>

bravitemplatesnews_list.html
<ul id="profile-results">
{% for n in news %}
<li>
<h3>{{ n.title }}</h3>
{{ n.text }}
</li>
{% endfor %}
</ul>
{% endblock %}

{% block footer %}
<a class="bt-action bt-action-edit" href="{{
url_for('create') }}">
<span>Create</span>
</a>
{% endblock %}

TEMPLATES – CREATE
{% extends "base.html" %}

{% block content %}

bravitemplatesnews_create.html
<h2>Create News</h2>
{% from "macros.html" import render_field %}
<form method="POST" action="." class="form">
{{ form.csrf_token }}
{{ render_field(form.title, class="input text") }}
{{ render_field(form.text, class="input text") }}
<input type="submit" value="Create">
</form>
{% endblock %}

{% block footer %}
<a class="bt-action bt-action-list" href="{{ url_for('all')
}}">
<span>News</span>
</a>
{% endblock %}

JINJA 2 – MACROS - DRY
{% macro render_field(field) %}
<div class="form_field">

bravitemplatesmacros.html
{{ field.label(class="label") }}
{% if field.errors %}
{% set css_class = 'has_error' +
kwargs.pop('class', '') %}
{{ field(class=css_class, **kwargs) }}
<ul class="errors">
{% for error in field.errors %}
<li>{{ error|e }}</li>
{% endfor %}
</ul>
{% else %}
{{ field(**kwargs) }}
{% endif %}
</div>
{% endmacro %}

VIEWS
from flask import request, flash, redirect, url_for, render_template
from braviapp import braviapp, db
from braviapp.forms import NewsCreateForm
from braviapp.models import News

@braviapp.errorhandler(404)
def not_found(error):
flash('You tried access a page that not exists')
return redirect(url_for('all'))

bravibraviappviews.py
@braviapp.route('/')
def all():
#from news_model import News
news = News.query.all()
return render_template('news_list.html', news=news)

@braviapp.route('/create/', methods=['GET', 'POST'])
def create():
form = NewsCreateForm(request.form)

# make sure data are valid
if form.validate_on_submit():

news = News(form.title.data, form.text.data)
# save on database
db.session.add(news)
db.session.commit()

flash('The news has been created successfully')
return redirect(url_for('all'))
return render_template('news_create.html', form=form)

CORE APP

bravibraviapp__init__.PY
# third party imports
from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy

# Initialize the app from Flask
braviapp = Flask(__name__)
braviapp.config.from_object('settings')

db = SQLAlchemy(braviapp)

# local application imports
from braviapp import views

SETTINGS FILE
import os
_basedir = os.path.abspath(os.path.dirname(__file__))

DEBUG = False

bravisettings.py
ADMINS = frozenset(['youremail@yourdomain.com'])
SECRET_KEY = 'SECRET_KEY_FOR_SESSION_SIGNING'

# Define the path of our database inside the root
application, where 'app.db' is the database's name
SQLALCHEMY_DATABASE_URI = 'sqlite:///' +
os.path.join(_basedir, 'app.db')
DATABASE_CONNECT_OPTION = {}

CSRF_ENABLED = True
CSRF_SESSION_KEY = 'SOMETHING_IMPOSSIBLE_TO_GUEES'

SQLALCHEMY

Helper to reset the database file

braviinitialize_db.py
from app import db

# Drop all tables from db file
db.drop_all()

# Create all tables on db file,
# copying the structure from the definition on the Models
db.create_all()

Running python initialize_db.py

RUNNING
Helper to initialize the application

braviinitialize_app.py
from braviapp import braviapp as application
application.run(debug=True,port=8080)

Running python initialize_app.py

LETS TRY

ANY
QUESTION?
Helpful links:
• http://flask.pocoo.org
• https://github.com/mitsuhi
ko/flask
• http://werkzeug.pocoo.org
• http://jinja.pocoo.org/docs
• http://www.sqlalchemy.org
• http://blog.maxcnunes.net
• http://www.google.com

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