Flask Cheat Sheet - And FREE samples

Editor -

This article is just another Flask Cheat Sheet that might help beginners to speed up their learning curve and the rest of our audience with some nice production-ready samples. Thanks for reading! TL;DR; links

  • Flask - the official website
  • Flask Tutorial - (Github) Content provided by experienced developers
Flask Pixel Lite - Free Flask Starter.

#1 - What is Flask

Flask is a lightweight WSGI web application framework. It is designed to make getting started quick and easy, with the ability to scale up to complex applications. Classified as a microframework,  Flask aims to keep the core of its framework small but highly extensible.

#2 - Install Flask

$ pip install Flask

#3 - Creating an isolated environment

python -m venv flask_env

Activate virtual environment

source source_env/bin/activate

Deactivate virtual environment

deactivate

#4 - A super simple Flask app

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return f'Hello from Flask!'

#5 - Start the app

$ env FLASK_APP=hello.py flask run
 * Serving Flask app "hello"
 * Running on http://127.0.0.1:5000/

#6 - Object-Based Configuration

Create a new config file in the project root:

PROJECT_ROOT/app/config.py

Add content using OOP and class inheritance

class BaseCfg(object):
    SECRET_KEY = 'SuperS3cretKEY_1222'
    DEBUG = False
    TESTING = False

class DevelopmentCfg(BaseCfg):
	DEBUG = True
	TESTING = True

class TestingCfg(BaseCfg):
	DEBUG = False
	TESTING = True

class ProductionCfg(BaseCfg):
    SECRET_KEY = 'HvFDDcfsnd__9nbCdgsada' 
	DEBUG = False
	TESTING = False

Let's use the configuration:

Update PROJECT_ROOT/app/__init__.py to use it

from flask import Flask
from app import config

app = Flask(__name__)
app.config.from_object(config.DevelopmentCfg) # <--- Magic line

#7 - Render page using Jinja

The Flask controller

from flask import Flask, render_template
app = Flask(__name__)


@app.route("/test")
def template_test():
    return render_template('template.html', my_string="Jinja Works!!")


if __name__ == '__main__':
    app.run(debug=True)

The HTML template

<html>
  <head>
    <title>Flask Template Example</title>
  </head>
  <body>
    <div class="container">
      <p>Result: {{my_string}}</p>
    </div>
  </body>
</html>

By accessing  http://localhost:5000/test in the browser, we should see:

Status: Jinja Works

#8 - Using Flask shell

$ flask shell

#9 - Define a model with SQLAlchemy using SQLite

Create PROJECT_ROOT/app/models.py with the following content:

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class User(db.Model):

    id       = db.Column(db.Integer,     primary_key=True)
    user     = db.Column(db.String(64),  unique = True)
    email    = db.Column(db.String(120), unique = True)
    password = db.Column(db.String(500))

    def __init__(self, user, email, password):
        self.user       = user
        self.password   = password
        self.email      = email

Update PROJECT_ROOT/app/config.py with the Database connection string

class BaseCfg(object):
    SECRET_KEY = 'SuperS3cretKEY_1222'
    DEBUG = False
    TESTING = False

    # This will create a file in <app> FOLDER
    SQLALCHEMY_DATABASE_URI = 'sqlite:///' + os.path.join(basedir, 'db.sqlite3')
    SQLALCHEMY_TRACK_MODIFICATIONS = False

Update PROJECT_ROOT/app/__init__.py to use the model

from flask_sqlalchemy import SQLAlchemy
...

db = SQLAlchemy  (app) # flask-sqlalchemy

The User  model can be created using flask shell

$ flask shell
>> from app import db
>> db.create_all()

The second method is to create the tables automatically at first request using a hook provided by Flask.

Update PROJECT_ROOT/app/__init__.py as below:

# Setup database
@app.before_first_request
def initialize_database():
    db.create_all()

#10 - List users via Flask shell

$ flask shell
>>> from app.models import User
>>> User.query.all()
# HERE we should see all users

#11 - Flask Database Migration

A migration means when we need to add, remove or update the type of a database table column. To safely reflect our update on the database, we need to "migrate" the DB schema.

Flask-Migrate

Install Flask-Migrate

$ pip install Flask-Migrate

Update PROJECT_ROOT/app/__init__.py as below:

...
app = Flask(__name__)
...
migrate = Migrate(app, db) # <- The magic line

If we execute a migration for the first time:

$ # This will create the migrations folder
$ flask db init

Migrate the schema - this will generate the SQL (no database change)

$ flask db migrate

Update the Database - using the SQL generated in the previous step

$ flask db upgrade

Let's see this theory applied to these open-source Flask samples:

Flask Pixel UI Kit - Sample #1

Open-Source Web App coded in Flask Framework - features:

  • UI Kit: Pixel UI kit by Themesberg
  • UI-Ready, Jinja2 templating
  • SQLite database, Flask-SQLAlchemy ORM
  • Session-Based auth flow (login, register)
Flask Pixel Lite - Open-source starter.

Flask Datta Able - Sample #2

Admin Dashboard generated by the AppSeed platform in Flask Framework on top of Datta Able (free version), a modern Bootstrap 4 dashboard template. The Flask codebase is provided with authentication, database, ORM and deployment scripts.

Flask Datta Able - Free Dashboard.

Flask Volt Free - Sample #3

Open-Source Flask Dashboard coded with basic modules, database, ORM and deployment scripts on top of Volt Dashboard (free version), a modern Bootstrap dashboard design.

Volt is a free and open source Bootstrap 5 Admin Dashboard featuring over 100 components, 11 example pages and 3 customized plugins. Volt does not require jQuery as a dependency meaning that every library and script's are jQuery free.

Flask Volt Dashboard - Open-source Dashboard.

Flask Argon - Sample #4

Argon Dashboard is built with over 100 individual components, giving you the freedom of choosing and combining. All components can take variations in color, that you can easily modify using SASS files.

You will save a lot of time going from prototyping to full-functional code, because all elements are implemented. This Dashboard is coming with pre-built examples, so the development process is seamless, switching from our pages to the real website is very easy to be done.

Flask Argon - Open-source Dashboard.
Thanks for reading! For more resources please access: