Chapter 5. The App Engine webapp Framework

Now that we have written a few low-level App Engine applications, it is time to begin to develop our application using the high-level Web Application (webapp) framework that is provided as part of Google App Engine.

This chapter reimplements the number guessing-application using the App Engine webapp framework instead of using low-level HTTP directly. The low-level capabilities that we used in the previous chapter are not gone—they are just hidden beneath a layer that has been added for our convenience.

The webapp library takes care of many of the mundane details of the HTTP interactions. The webapp framework handles all details, like parameter parsing, multipart parameter formats, and so on.

Although using the webapp framework may initially look a little more complex than the lower-level code, in the long run, your web applications will be far smaller and you won’t end up reading RFC documents to make sure that your program is compliant with the subtle details of the HTTP protocol. Your programs won’t break because you did not notice some small detail in the protocol until a user started using a different browser than the ones that you used for testing.

A Trivial App Engine Application

Recall the very first example of the web application; it consisted of two files. The first file is app.yaml:

application: ae-00-trivial
version: 1
runtime: python
api_version: 1

handlers:
- url: /.*
  script: index.py

The second file is index.py and consists of three ...

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