Learn Flask Web Development in 90 minutes, it will use docker as development environment, CodingWithMe style

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