Flask is a microframework for Python web development that makes it easy to build web applications. It helps separate Python code from HTML templates, generates RESTful URLs, and has a flexible MVC design pattern. Flask applications can be used to summarize and share information, promote research, and blog. The documentation for Flask and its templating engine Jinja2 is very good.

1. Building a local web application
with Flask
Mickaël Mendez - Tech Talk - December 21, 2016

2. Why would you develop a web
application ?
● Main goal: Summarize and Display information
● Share results with collaborators
● Promote your research
● Blogging
● Why not? Python makes it very easy!

3. What not to do
● Don’t write html tags within your Python
script. It will become impossible to read as the
project grows
● Don’t write URLs manually. It requires
unnecessary engineering to keep track of the
current location and format the links properly

4. Some Numbers
● 800 Lines of Code
● 450 Lines of Code
● 1500 Lines of Code (Test)
● 1000 Lines of Code (Test)
● 200 A4 pages of Documentation
● 140 A4 pages of Documentation
2011-2015

5. Instead use Flask
● Micro-framework for Python web development
● RESTful URL mapping
● Contains development server and debugger
● Flexible MVC design pattern (Jinja2)
● Very good documentation

6. Hello World

7. Hello World

8. Templates
app.py
templates/hello.tpl
static/style.css

9. Templates

10. Templates (Jinja2)
For loops
If statements

11. Variables types

12. Template inheritance
Child: templates/hello.tpl
Parent: templates/layout.tpl

13. Plotting
app.py
templates/plot.tpl

14. Extensions
● Frozen-Flask
● Flask-SQLAlchemy
● Flask-Admin
● Flask-Heroku
● Flask-Babel
● ...

15. Good links
Flask4scientists:
http://hplgit.github.io/web4sciapps/doc/pub/web4sa_solarized.html
Flask Documentation: http://flask.pocoo.org/docs/0.11/
Jinja2 Documentation: http://jinja.pocoo.org/docs/dev/

16. Summary
● Flask helps generating a web application
○ Separate Python from HTML
○ Generate URLS
○ Lightweight - It does not store the web pages on disk
● Visualize and share your results
● Very well documented - maybe on of the best documentation
● Few dependencies
● Works with Python 3.3