How to use Python main() function in GAE (Google App Engine)?

Question

I\'d like to use a main() function in my GAE code
(note: the code below is just a minimal demonstration for a much larger program, hence the need for a

Answer 1

GAE apps are not designed to be standalone apps, a main() function doesn't make a lot of sense for them.

Basically GAE apps are really just collections of handler code and rules/configurations designed to extend and customize the behaviour of the generic GAE infra/sandbox code so that it behaves your app. You can see that from your backtrace - other code is invoking your handler code (and the stack before reaching your code can be a lot deeper than that).

In your particular case the app variable must be a global in main.py to match the script: main.app config line in the app.yaml config file. This is what the traceback is about.

As for organizing the code for huge apps, there are other ways of doing it:

• splitting the app in multiple modules/services, each with their own app.yaml config file. For example: Can a default service/module in a Google App Engine app be a sibling of a non-default one in terms of folder structure?

• splitting a service/module into multiple "scripts" - primary entry points into the app.yaml file similar to your main.py file, each with their own app config` - which really are just mappers between routes and handlers. For example: App Engine throws 404 Not Found for any path but root

• splitting the handlers for one app mapper into multiple files, using webapp2's lazy loaded handler technique. Examples:

  • App Engine: Few big scripts or many small ones?
  • What determines start up time of dynamic instance and can it vary between weeks if code is same

In an extreme case a main.py file could contain just the app variable - that is really the only requirement.