Programming Google App Engine with Python

Chapter 18. The Django Web Application Framework

As with all major categories of software, web applications have a common set of problems that need to be solved in code. Most web apps need software to interface with the server’s networking layer, communicate using the HTTP protocol, define the resources and actions of the application, describe and implement the persistent data objects, enforce site-wide policies such as access control, and describe the browser interface in a way that makes it easily built and modified by designers. Many of these components involve complex and detailed best practices for interoperating with remote clients and protecting against a variety of security vulnerabilities.

A web application framework is a collection of solutions and best practices that you assemble and extend to make an app. A framework provides the structure for an app, and most frameworks can be run without changes to demonstrate that the initial skeleton is functional. You use the toolkit provided by the framework to build the data model, business logic, and user interface for your app, and the framework takes care of the details. Frameworks are so useful that selecting one is often the first step when starting a new web app project.

Notice that App Engine isn’t a web application framework, exactly. App Engine provides scaling infrastructure, services, and interfaces that solve many common problems, but these operate at a level of abstraction just below most web app frameworks. A better ...