google app engine in 40 minutes (the absolute essentials)

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Google App Engine in 40 Minutes

(The Absolute Essentials)

Paul Barry – Institute of Technology, Carlow in Ireland

PyCon Ireland 2011

Grab the slides:

http://paulbarry.itcarlow.ie/GAE.pdf

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The Absolute Essentials in 40 Minutes...

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What is Google App Engine?

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Cloud-based Application Deployment Environment

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Integrated Collection of Google APIs

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Guido's Playground

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Is App Engine “just another framework”?

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It is all about your data...

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Think of App Engine as a highly scalable,distributed database server that you can program

with Python 2.5...

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Think of App Engine as a highly scalable,distributed database server that you can program

with Python 2.5...

and (cough) Java and (cough, cough) Go

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MVC

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Let's solve a real problem...

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Step 1

Download the SDK from:

http://code.google.com/appengine/

and sign-up for an App Engine account ID

http://code.google.com/appengine/

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Step 2

Create a new project...

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...by creating an app.yaml file

application: dwwgapp version: 1 runtime: python api_version: 1

handlers: - url: /static static_dir: static

- url: /.* script: dwwgapp.py

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Step 3

Model Your Data

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Create dwwgDB.py (1 of 3)

from google.appengine.ext import db

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class Sighting(db.Model):

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class Sighting(db.Model):name = db.StringProperty()email = db.StringProperty()date = db.DateProperty()time = db.TimeProperty()location = db.StringProperty()fin_type = db.StringProperty()whale_type = db.StringProperty()blow_type = db.StringProperty()wave_type = db.StringProperty()

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Step 4

Define your UI in HTML

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The header.html template

<html> <head>

<title>{{ title }}</title> </head> <body>

<h1>{{ title }}</h1>

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The footer.html template

<p> {{ links }} </p> </body>

</html>

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The form_start.html template

<form method=”POST” action=”/”> <table>

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The form_end.html

<tr><th> </th><td><input type="submit"

value="{{ sub_title }}"></td></tr>

</table> </form>

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Render some HTML

from google.appengine.ext.webapp import template

html = template.render('templates/header.html', {'title': 'Report a Possible Sighting'})

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Rendering a Page


html = template.render('templates/header.html',{'title': 'Report a Possible Sighting'})

html = html + template.render('templates/form_start.html', {})

# Do something in here to render the form?!?!?!?!?!?!?

html = html + template.render('templates/form_end.html',{'sub_title': 'Submit Sighting'})

html = html + template.render('templates/footer.html', {'links': ''})

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Step 5

Write code to render your form

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Django Forms to the Rescue!

from google.appengine.ext.db import djangoforms

import dwwgDB

class SightingForm(djangoforms.ModelForm):class Meta:

model = dwwgDB.Sighting

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Rendering a Page, Again


html = template.render('templates/header.html',{'title': 'Report a Possible Sighting'})

html = html + template.render('templates/form_start.html', {})

html = html + str(SightingForm())

html = html + template.render('templates/form_end.html',{'sub_title': 'Submit Sighting'})

html = html + template.render('templates/footer.html', {'links': ''})

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Step 6

Tie it all together with logic

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You need to start your webapp

from google.appengine.ext import webappfrom google.appengine.ext.webapp.util import run_wsgi_app

…

app = webapp.WSGIApplication([('/.*', SightingInputPage)], debug=True)

def main(): run_wsgi_app(app)

if __name__ == '__main__': main()

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Remember the app.yaml file?



- url: /.* script: dwwgapp.py

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Put this code in dwwgapp.py

from google.appengine.ext import webappfrom google.appengine.ext.webapp.util import run_wsgi_app

…

app = webapp.WSGIApplication([('/.*', SightingInputPage)], debug=True)

def main(): run_wsgi_app(app)

if __name__ == '__main__': main()

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What's this SightingInputPage thing?

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class SightingInputPage(webapp.RequestHandler): def get(self): html = template.render('templates/header.html',

{'title': 'Report a Possible Sighting'}) html = html + template.render('templates/form_start.html', {}) html = html + str(SightingForm()) html = html + template.render('templates/form_end.html',

{'sub_title': 'Submit Sighting'}) html = html + template.render('templates/footer.html', {'links': ''}) self.response.out.write(html)

Responding to a GET Request

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Step 7

Take your local app for a spin

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Click the “Run” button...

or

$ dev_appserver.py dwwgapp

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Ta Da! :-(

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Looks kinda shitty, doesn't it?

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Add a little CSS goodness..

<link type="text/css" rel="stylesheet" href="/static/dwwg.css" /><link type="text/css" rel="stylesheet" href="/static/styledform.css" />

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...and some code to dwwgDB.py

_FINS = ['Falcate', 'Triangular', 'Rounded'] _WHALES = ['Humpback', 'Orca', 'Blue', 'Killer', 'Beluga', 'Fin', 'Gray', 'Sperm'] _BLOWS = ['Tall', 'Bushy', 'Dense'] _WAVES = ['Flat', 'Small', 'Moderate', 'Large', 'Breaking', 'High']

...

location = db.StringProperty(multiline=True)fin_type = db.StringProperty(choices=_FINS) whale_type = db.StringProperty(choices=_WHALES) blow_type = db.StringProperty(choices=_BLOWS) wave_type = db.StringProperty(choices=_WAVES)

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Ta Da! :-)

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Step 8

Do something with your data

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You need to POST data!

POST data with put()

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def post(self):

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def post(self): new_sighting = dwwgDB.Sighting()

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def post(self): new_sighting = dwwgDB.Sighting() new_sighting.name = self.request.get('name') new_sighting.email = self.request.get('email') new_sighting.date = self.request.get('date') new_sighting.time = self.request.get('time') new_sighting.location = self.request.get('location') new_sighting.fin_type = self.request.get('fin_type') new_sighting.whale_type = self.request.get('whale_type') new_sighting.blow_type =self.request.get('blow_type') new_sighting.wave_type = self.request.get('wave_type')

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def post(self): new_sighting = dwwgDB.Sighting() new_sighting.name = self.request.get('name') new_sighting.email = self.request.get('email') new_sighting.date = self.request.get('date') new_sighting.time = self.request.get('time') new_sighting.location = self.request.get('location') new_sighting.fin_type = self.request.get('fin_type') new_sighting.whale_type = self.request.get('whale_type') new_sighting.blow_type =self.request.get('blow_type') new_sighting.wave_type = self.request.get('wave_type')

new_sighting.put()

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html = template.render('templates/header.html', {'title': 'Thank you!'}) html = html + "<p>Thank you for providing your sighting data.</p>" html = html + template.render('templates/footer.html', {'links': 'Enter <a href="/">another sighting</a>.'}) self.response.out.write(html)

And don't forget to say “Thanks!”

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Step 9

Deploy to Google's cloud

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Click the “Deploy” button...

or

$ appcfg.py upload dwwgapp/

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http://dwwgapp.appspot.com

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Step 10

Realise your not done...

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Damn That Spam!

Some smart-alec posted a sightingof a Great White Shark on the top

of Mount Leinster...

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What to do?

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A tiny config tweak to app.yaml...



- url: /.* script: dwwgapp.py login: required

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...and two tiny code changes

Add this to the dwwgDB.py model:

which_user = db.UserProperty()

Add this to your post() method in dwwgapp.py:

new_sighting.which_user = users.get_current_user()

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http://dwwgapp.appspot.com

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http://appengine.google.com

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And after all that,what do you end up with?

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Happy Clients!

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Want to learn moreabout this talk's example code?

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Head First Python

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Don't forget to check out the App Engine Tutorial on Sunday

with Seán Murphy