This is a demo of Flask for a lecture in an intro to web dev class. If you're looking to learn Flask I would instead recomment you follow this tutorial.

The finished code for this demo is available here: releases/tag/1.6-errorhandling-page

• We've seen PHP, but there's many other languages/frameworks for web apps out there.
  • PHP is widely used by Facebook.

A library that let's us create web applications / sites using using python. (If you've ever heard of Django it's similar but more bare-bones.)

• Pinterest Uses for apis - serves over 12 billion requests per day
• LinkedIn uses for internal tools

• Don't need a php file for every page.
• Can use python, language we're familar with, and any python libraries we want
• Jinja templating provides a tool for html reuse

1. Install some needed packages

   sudo apt-get update
   sudo apt-get install python-dev python-pip virtualenvwrapper git
   cat >> ~/.bashrc << EOF
     export WORKON_HOME=$HOME/.virtualenvs
     export PROJECT_HOME=$HOME/dev
     source /usr/share/virtualenvwrapper/virtualenvwrapper.sh
   EOF
   source ~/.bashrc

2. Download the starting source code

   mkdir -p ~/dev/
   cd ~/dev/
   git clone https://github.com/Graham42/flask-tutorial flask-intro
   cd flask-intro/
   git checkout 1.0-Hello-World

3. Setup for this project: create virtual python environment, install Flask

   mkvirtualenv flask-demo
   cd ~/dev/flask-intro
   setvirtualenvproject
   pip install Flask
   deactivate

4. Any time you want to work on this project just run workon flask-demo to activate the virtual python environment we created for this project, which now has Flask installed

There are several tags noted in the following, you can switch to that version of the code by running git checkout <tag_name>

The starting code you've downloaded is a basic Hello World web app. To run this web app, let's open a terminal window.

workon flask-demo
python server.py

You should be able to view this webpage at http://localhost:3000

Tag: 1.0-Hello-World

The Jinja documentation has an example of what Jinja looks like. This is what we'll be using in our HTML files.

Tag: 1.1-IF-demo

Tag: 1.2-loop-demo

Unlike PHP, our pages don't need to end in .php. Let's add another page. First, in our demo_app/__init__.py

@app.route('/other_page/')
def other():
    return render_template('other_page.html')

Then add the html file. Now can see this other page when we go to /other_page.

Tag: 1.3-new-page

About this html file, we've now got a bunch of shared code between our main page and this other one. Jinja let's us create a base page and extend it. We can reuse common html code instead of copy pasting all over the place.

Tag: 1.4-template-inheritance

Cool thing that is hard to do in PHP.

Tag: 1.5-news-url-vars

More about error pages

Might have broken links, or maybe someone tries to go to a page that doesn't exist.

Tag: 1.6-errorhandling-page

Many python libraries available to access whatever database you want, MySQL, PostgreSQL, etc

If I've peaked your interest, should definitely check out the Flask Mega Tutorial