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Flask Cheat Sheet - And FREE samples

sm0ke profile image Sm0ke Originally published at blog.appseed.us ・5 min read

Hello Coders,

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



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
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3# - Creating an isolated environment

$ python -m venv flask_env
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Activate virtual environment

$ source flask_env/bin/activate
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Deactivate virtual environment

$ deactivate
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4# - A super simple Flask app

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return f'Hello from Flask!'
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5# - Start the app

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

<html>
  <head>
    <title>Flask Template Example</title>
  </head>
  <body>
    <div class="container">
      <p>Result: {{my_string}}</p>
    </div>
  </body>
</html>
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By accessing http://localhost:5000/test in the browser, we should see:

Status: Jinja Works


8# - Using Flask shell

$ flask shell
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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
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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
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Update PROJECT_ROOT/app/__init__.py to use the model:

from flask_sqlalchemy import SQLAlchemy
...

db = SQLAlchemy  (app) # flask-sqlalchemy
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The User tables can be created using flask shell:

$ flask shell
>>> from app import db
>>> db.create_all()
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The second method is to create the tables automatically at the 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()
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10# - List users via Flask shell

$ flask shell
>>> from app.models import User
>>> User.query.all()
# HERE we should see all users 
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Let's see this theory applied to these open-source Flask samples:


Flask Pixel UI Kit

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 UI Kit - Open-source Flask starter, provided by AppSeed.


Flask Datta Able

Flask Dashboard generated by the AppSeed platform 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.


Flask Volt Free

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 Free.


Flask Dashboard Argon

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 Dashboard.


Thanks for reading! For more resources please access:


Thank you! Btw, my (nick) name is Sm0ke and I'm pretty active also on Twitter.

Discussion (9)

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crearesite profile image
WebsiteMarket

Nice, Thanks!

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leviathanprogramming profile image
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Sm0ke Author

Yw, Thank you for reading this post.

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yokotobe

Thanks for sharing

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ui-themes

Cool. Would be nice to have something related to Flask Migration.

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Sm0ke Author

Noted! I will add the content asap.