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Boilerplate project template for running Flask on Google App Engine
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Flask on App Engine Project Template

Boilerplate project template for running a Flask-based application on Google App Engine (Python)

About Flask

Flask is a BSD-licensed microframework for Python based on Werkzeug, Jinja2 and good intentions.

See for more info.


  1. Download this repository via git clone or download the tarball at
  2. Copy the src/ folder to your application's root folder
  3. Set the application id in src/app.yaml
  4. Configure datastore models at src/application/
  5. Configure application views at src/application/
  6. Configure URL routes at src/application/
  7. Configure forms at src/application/
  8. Add the secret keys for CSRF protection by running the script at src/application/, which will generate the secret keys module at src/application/

Note: Copy the .gitignore file from the tarball folder's root to your git repository root to keep the secret_keys module out of version control.

Or, add the following to your .(git|hg|bzr)ignore file

  # Keep secret keys out of version control

Front-end Customization

  1. Customize the main HTML template at src/application/static/templates/base.html
  2. Customize CSS styles at src/application/static/css/main.css
  3. Add custom JavaScript code at src/application/static/js/main.js
  4. Customize favicon at src/application/static/img/favicon.ico
  5. Customize 404 page at src/aplication/templates/404.html

Testing the Application

To test the application using App Engine's development server, use src/

Assuming the latest App Engine SDK is installed, the test environment is available at http://localhost:8080

Deploying the Application

To deploy the application to App Engine, use update update src/

The application should be visible at http://{YOURAPPID}

Folder structure

The App Engine app's root folder is located at src/.

  |-- app.yaml (App Engine config file)
  |-- application (application code)
  |-- index.yaml (App Engine query index definitions)
  |-- (Main App Engine handler)
  |-- packages (Flask and third-party zip packages)
      |-- (Flask core)
      |-- flaskext (Flask extensions go here)
      |-- (template engine)
      |-- (JSON utility required by Jinja2)
      |-- werkzeug (WSGI utilities for Python-based web development)
      |-- werkzeug_debugger_appengine (enables Werkzeug's interactive debugger for App Engine)
      `-- (Jinja2-compatible web form utility)

The application code is located at src/application.

  |-- (initializes Flask app)
  |-- (decorators for URL handlers)
  |-- (web form models and validators)
  |-- (App Engine datastore models)
  |-- (settings for Flask app)
  |-- static
  | |-- css
  | | `-- main.css (custom styles)
  | |-- img
  | | |-- favicon.ico (replace with custom favicon)
  | | `-- favicon.png
  | `-- js
  |   |-- main.js (custom javascript)
  |   `-- modernizr-2.min.js (HTML5 enabling and detection)
  |-- templates
  | |-- 404.html (not found page)
  | |-- 500.html (server error page)
  | |-- base.html (master template)
  | |-- list_examples.html (example list-based template)
  | `-- new_example.html (example form-based template)
  |-- (unit tests)
  |-- (URL dispatch routes)
  `-- (Handlers for URL routes defined at

Removing Extended Attributes (@ flag)

A few of the files in the source tree were uploaded (with apologies) to GitHub with extended attributes (notice the '@' symbol when running ls -al).

To remove the extended attributes, use xattr -rd at the root of the src/ folder.

  xattr -rd .
  xattr -rd com.macromates.caret .

Note: Windows users may safely ignore the xattr fix


See licenses/ folder

Package Versions

  • Flask: 0.6.1
  • Flask-WTF: 0.5.2
  • Jinja2: 2.5.5
  • simplejson: 2.1.6
  • Werkzeug: 0.6.2
  • WTForms: 0.6.2
  • Modernizr: 2.0


Project template layout was heavily inspired by Francisco Souza's gaeseries Flask project

HTML5-based main template (templates/base.html) extracted from HTML5 Boilerplate

HTML5 detection provided by Modernizr 2 (configured with all features)

CSS reset, fonts, grids, and base styles provided by YUI 3

Project layout improvements (zip archives/zipimport) contributed by Stochastic Technologies.

Werkzeug's Interactive Debugger enabled for App Engine using Naitik Shah's werkzeug-debugger-appengine utility.

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