Project structure for Google App Engine

Question

I started an application in Google App Engine right when it came out, to play with the technology and work on a pet project that I had been thinking about for a long time bu

Answer 1

My usual layout looks something like this:

• app.yaml
• index.yaml
• request.py - contains the basic WSGI app
• lib
  • __init__.py - common functionality, including a request handler base class
• controllers - contains all the handlers. request.yaml imports these.
• templates
  • all the django templates, used by the controllers
• model
  • all the datastore model classes
• static
  • static files (css, images, etc). Mapped to /static by app.yaml

I can provide examples of what my app.yaml, request.py, lib/init.py, and sample controllers look like, if this isn't clear.

Answer 2

I think the first option is considered the best practice. And make the code folder your first package. The Rietveld project developed by Guido van Rossum is a very good model to learn from. Have a look at it: http://code.google.com/p/rietveld

With regard to Django 1.0, I suggest you start using the Django trunk code instead of the GAE built in django port. Again, have a look at how it's done in Rietveld.

Answer 3

I am not entirely up to date on the latest best practices, et cetera when it comes to code layout, but when I did my first GAE application, I used something along your second option, where the code and templates are next to eachother.

There was two reasons for this - one, it kept the code and template nearby, and secondly, I had the directory structure layout mimic that of the website - making it (for me) a bit easier too remember where everything was.

Answer 4

I like webpy so I've adopted it as templating framework on Google App Engine.
My package folders are typically organized like this:

app.yaml
application.py
index.yaml
/app
   /config
   /controllers
   /db
   /lib
   /models
   /static
        /docs
        /images
        /javascripts
        /stylesheets
   test/
   utility/
   views/

Here is an example.

Answer 5

First, I would suggest you have a look at "Rapid Development with Python, Django, and Google App Engine"

GvR describes a general/standard project layout on page 10 of his slide presentation.

Here I'll post a slightly modified version of the layout/structure from that page. I pretty much follow this pattern myself. You also mentioned you had trouble with packages. Just make sure each of your sub folders has an __init__.py file. It's ok if its empty.

Boilerplate files

• These hardly vary between projects
• app.yaml: direct all non-static requests to main.py
• main.py: initialize app and send it all requests

Project lay-out

• static/*: static files; served directly by App Engine
• myapp/*.py: app-specific python code
  • views.py, models.py, tests.py, __init__.py, and more
• templates/*.html: templates (or myapp/templates/*.html)

Here are some code examples that may help as well:

main.py

import wsgiref.handlers

from google.appengine.ext import webapp
from myapp.views import *

application = webapp.WSGIApplication([
  ('/', IndexHandler),
  ('/foo', FooHandler)
], debug=True)

def main():
  wsgiref.handlers.CGIHandler().run(application)

myapp/views.py

import os
import datetime
import logging
import time

from google.appengine.api import urlfetch
from google.appengine.ext.webapp import template
from google.appengine.api import users
from google.appengine.ext import webapp
from models import *

class IndexHandler(webapp.RequestHandler):
  def get(self):
    date = "foo"
    # Do some processing        
    template_values = {'data': data }
    path = os.path.join(os.path.dirname(__file__) + '/../templates/', 'main.html')
    self.response.out.write(template.render(path, template_values))

class FooHandler(webapp.RequestHandler):
  def get(self):
    #logging.debug("start of handler")

myapp/models.py

from google.appengine.ext import db

class SampleModel(db.Model):

I think this layout works great for new and relatively small to medium projects. For larger projects I would suggest breaking up the views and models to have their own sub-folders with something like:

Project lay-out

• static/: static files; served directly by App Engine
  • js/*.js
  • images/*.gif|png|jpg
  • css/*.css
• myapp/: app structure
  • models/*.py
  • views/*.py
  • tests/*.py
  • templates/*.html: templates

Answer 6

I implemented a google app engine boilerplate today and checked it on github. This is along the lines described by Nick Johnson above (who used to work for Google).

Follow this link gae-boilerplate