Programming Lecture 2nd - Flask and Heroku in Python -

Entrepreneurship open school
Programming Course
-Flask and Heroku in Python-
Thursday, May 18, 2017
Tokyo, Japan
Naoki Watanabe
Thursday, May 18. 2017 Programming course 1

Goal of courses: Run Lean and create app
• Search what people what
• Lauch MVP (Minimum Viable Product)

Goals of today’s lecture
• Install Python with conda
• Create simple web application with Flask
• Publish your application freely on Heroku via Git

Contents
• Install Anaconda powered by Python
• Learn basic Python grammar
• Follow Flask, web framework, tutorial
• Create your web application powered by Flask
• Public your application

What is Python and why?
• It’s a programming language.
• Very simple and nice to learn for beginner
• Many company use it (Google’s Gmail, Map, Earth, YouTube).
• It goes with data science, machine learning and deep learning

Install Python via Conda
• Conda is package controller
• Anaconda is conda and some packages.
• Search “Anaconda install” on Google.
• It is tough to go with python on Windows, and windows user
has to install anaconda, not from python official page.
• There is also miniconda, smaller alternative to anaconda.

Create a virtual environment
$ conda -V
$ conda create –n venv
$ source activate venv
(venv) $
To deactivate, $ source deactivate
-n: specifies the name of a virtual environment
To activate/deactivate on Windows, remove source.
$ activate venv

For beginner, keep three things in mind
• Codes goes from up to down.
• You can switch code by if else clause.
• You can iterate by for loop.
You will see how to in the next slides.

sample.py – print(1) – 1.1
Make a file sample.py that contains only
print(1)

sample.py – print(1) 1.2
Run Terminal (Mac or Linux) or Command Prompt (Windows)
$ cd path/to/folder/where/sample.py/is
$ python sample.py
Then, is 1 printed? Your first python code ran perfectly !

sample.py 2 – string is what quoted -

sample.py 3 – list -

sample.py 4 – loop -

sample.py 5 – if else clause -

sample.6 - function

Q. Fizz Buzz
• Count a number from 1 to 100, but any number divisible by
three is replaced by the word fizz and any divisible by five by
the word buzz. Numbers divisible by both become fizz buzz
1, 2, Fizz, 4, Buzz, Fizz, 7, 8, Fizz, Buzz, 11, Fizz, 13, 14, Fizz
Buzz, 16, 17, Fizz, 19, Buzz, Fizz, 22, 23, Fizz, Buzz, 26, Fizz, 28,
29, Fizz Buzz, 31, 32, Fizz, 34, Buzz, Fizz, ...
To get reminar, use %. Ex. 5%2. To diverge into three or more,
use if…elif…else.

A. FizzBuzz

A2. FizzBuzz (one line)

Create simple web app with flask
• Flask is a framework to make a website easily.
• You can make a web app just in five lines.
• Pinterest, LinkedIn, and Flask community page use it.
• The most popular Python web framework on GitHub
(mid2016)
• The next slides follows tutorial
http://flask.pocoo.org/docs/0.12/quickstart/

hello.py #1 Go to http://localhost:5000

hello.py #2 http://localhost:5000/hello

hello.py #3 http://localhost:5000/user/bob
Also go to http://localhost:5000/post/999

hello.py #4.1 Render html

hello.py #4.2 make templates/hello.html
/hello.py
/templates
/hello.html

hello.html #4.3 edit hello.html

Hypothesis #5.0
• Some people love cat and want to see as many cat gifs.
• You are going to create MVP.
• Application just shows cat gif.

cat.py #5.1 Create your own app!
/cat.py
/templates
/cat.html

cat.py #5.2

We use cat API #5.3
• Application Program
Interface (API) is set of tools
for applications.
• Many service provide API.
• You can use Google Map API,
YouTube API, Amazon API
and many others to create
your web service.

cat.html #5.4

#5.6 Run application
• It shows a cat gif randomly.

cat.py #5.7 Show nice nine gif animations

cat.html #5.8 Show nice nine gif anis

#5.9 http://localhost:5000

cat.py #5.11 powered by Bootstrap

Get Bootstrap link #5.12
• Search “Bootstrap getting started” on Google

cat.html #5.13 powered by Bootstrap

#5.14 Run app

#5.15 See it’s responding

What is Heroku? #1
• You can publish your app on Heroku
• Heroku is free to use (They also have a paid plan.)
• Before start, remove debug=True in cat.py

Create Heroku account and install #2
• Search “Heroku” on Google
• Create an account (choose Python)
• Install heroku CLI (This may take a while)
• For Mac, brew install heroku
• For Windows, search “Heroku CLI windows”. Download and install it.
• Close and start terminal (command prompt on Win) again

Create a runtime.txt #3
$ echo python-3.6.1 > runtime.txt
Let runtime.txt contain only above one line.
https://devcenter.heroku.com/articles/python-runtimes
/runtime.txt
/requirements.txt
/cat.py
/templates
/cat.html

Create a requirements.txt #4.1
$ pip freeze > requirements.txt
, but change into conda==4.3.16 as Heroku does’nt newer.
Make requirements.txt contain just above two lines.
/cat.py
/requirements.txt
/templates
/cat.html

My requirements.txt #4.2
beautifulsoup4==4.6.0
conda==4.3.16
Flask==0.12.2
gunicorn==19.7.1
itsdangerous==0.24
Jinja2==2.9.6
MarkupSafe==1.0
requests==2.12.4
Werkzeug==0.12.2

Create a Procfile # 5
$ echo web: gunicorn cat:app --log-file=- > Procfile

Login to Heroku and create app #6.1
$ heroku
$ heroku create
You can access URL shown

Push app on Heroku #6.2
$ git init
$ git add .
$ git status
$ git commit –m “Initialize repository”
$ git log
$ git push heroku master

Upload to Heroku #6.3
$ git push heroku master
$ heroku ps:scale web=1
$ heroku ps
$ heroku open

See your app #7

Create a repo on GitHub #8.1 if you want

Push to your GitHub Repository
Copy Git URL for “git remote add origin <URL>”
$ git remote add origin
https://github.com/<username>/<repository_name>.git
$ git push origin master

GitHub Repository #8

Bibliography
• https://immense-escarpment-11300.herokuapp.com/
• http://qiita.com/kounoike/items/6fc31fe051e5d688f136
• http://flask.pocoo.org/docs/latest/quickstart/
• https://devcenter.heroku.com/articles/getting-started-with-
python
• http://michaeljgilliland.blogspot.jp/2013/01/one-line-fizz-
buzz-test-in-python.html

That’s all. Thank you, folks.

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