The document outlines a framework for learning Flask, a microframework for Python, through a series of exercises including creating a basic app, routing, using templates, handling forms, and integrating a database with Flask-SQLAlchemy. It provides detailed instructions and tips for setting up the environment using Docker and engaging with various Flask functionalities. Additionally, it emphasizes the simplicity and power of Flask alongside other web technologies.

1. Larry cai <larry.caiyu@gmail.com>

2. Agenda
 Introduction
 Exercise 1: Flask’s “Hello World”
 Exercise 2: Routing for URL
 Exercise 3:Template (Jinja2)
 Exercise 4: Handle form
 Exercise 5: Database (Flask-SQLAlchemy)
 Reference
Learn flask in 90 minutes2 04/13/15
http://flask.pocoo.org/

3. Environment Preparation (docker)
 Boot2docker Installer (127M)
 Contains latest docker already, fast
 Container persistence via disk automount on /var/lib/docker
 $ docker -v
 User/Passwd: docker/tcuser (192.168.59.103)
 Download python:2 docker image
 $ docker pull python:2
 (Windows/Mac) Clone the code from github to your user
directory (~/git)
https://github.com/larrycai/codingwithme-flask
 Notepad++ & MobaXterm are recommended
Learn flask in 90 minutes3 04/13/15
http://boot2docker.io/

4. Introduction
 Flask is a microframework for Python based on
Werkzeug, Jinja 2 and good intentions.
 Similar to Play framework (Java/Scala), Sinatra (Ruby),
 Also Django vs Ruby on Rails vs Grail ..
Learn flask in 90 minutes4 04/13/15
http://flask.pocoo.org/

5. Exercise 1: Hello World
 Run first app inside docker environment
$ cd /c/Users/<id>/git/codingwithme-flask
$ docker run -it -v $PWD:/code -w /code -p 5000:5000 python:2 bash
# pip install flask
# cd exer1
# python app.py
* Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
192.168.59.3 - - [08/Apr/2015 15:50:29] "GET / HTTP/1.1" 200 -
192.168.59.3 - - [08/Apr/2015 15:50:29] "GET /favicon.ico HTTP/1.1" 404
-
 Browse: http://192.168.59.103:5000
 Edit the app.py to print your name “Hello
Larry” instead of “Hello World”
 Tips: edit in windows, don’t need restart
(debug=True) Learn flask in 90 minutes5 04/13/15

6. Routing/Redirect for URL
 Routing is defined by the route() decorator
 Dynamic routing using variable
 Redirect to another one using redirect, url_for
Learn flask in 90 minutes6 04/13/15

7. Exercise 2: Routing
 Implement /user to suggest use /user/<name>
 Implement /user/<name>, say hello if it is Larry, otherwise
say byebye
 Redirect /users/ to /user with error indication
# cd ../exer2
# python app.py
 Tips: check console log redirect 302 (redirect)
Learn flask in 90 minutes7 04/13/15

8. Template using Jinja2
 Flask configures the Jinja2 template engine automatically
 render_template
 Jinja2 is a full featured template engine for Python.
 Map python variable into template
 Template inheritance makes it possible to use the same
or a similar layout for all templates
Learn flask in 90 minutes8 04/13/15
http://jinja.pocoo.org/

9. Exercise 3: Jinja2 Template
 Use template instead of string for function hello_user()
# cd ../exer3
# python app.py
Learn flask in 90 minutes9 04/13/15

10. Handle form
 request.form is good enough for simple form
 Flask-WTF module can be used if needed complex
handling for the form (like validation)
Learn flask in 90 minutes10 04/13/15

11. Exercise 4: Web Form
 Provide form to user as started in user()
# cd ../exer4
# python app.py
 Check whether it is in allowed list and redirect to hello
page, otherwise show error message (“xxx, who bring
you here ?”)
 Tips: form is normal html form
Learn flask in 90 minutes11 04/13/15

12. Database ORM – Flask-SQLAlchemy
 Flask-SQLAlchemy is extension provides a wrapper
for the SQLAlchemy project, which is an Object
Relational Mapper or ORM
 Support different database (SQLite, MySQL, Postgre ….)
 Command Steps
 Define database
 The data model
 Create database
 Operate database ..
Learn flask in 90 minutes12 04/13/15

13. Exercise 5: ORM for Database
 Start with base comments app and understand
# cd ../exer5
# pip install flask-sqlalchemy
# python app.py
 Add extra item “nickname”
 Bonus:
Initialize the database (/create) if database doesn’t exist (remove
*.sqlite3 first)
Reset the database (/drop)
Tips:
db.create_all(app=app) & db.drop_all(app=app)
Learn flask in 90 minutes13 04/13/15
example is based on: http://runnable.com/UhcUVQ7XwdEqAAPg/using-
sqlalchemy-in-flask-for-python

14. Summary
 Flask is python web framework, similar exists in other
language
 Routing/Template/Form/Database are the base
knowledge.
 Simple but powerful (together with css/javascript)
 Learn more sample, and try to build your own !!
Learn flask in 90 minutes14 04/13/15

15. Reference
 http://flask.pocoo.org/
 Book: Flask Web Development:
http://oreilly.com/catalog/9781449372620/
 Miguel Grinberg’s Blog: http://blog.miguelgrinberg.com/
 Base example for exer5 :
http://runnable.com/UhcUVQ7XwdEqAAPg/using-sqlalchemy-
in-flask-for-python

Learn flask in 90 minutes15 04/13/15

16. ChangeLog
 2015/04/12: first release
 2015/04/13: after first pilot, summary is added
Learn docker in 90 minutes16 04/13/15