How to check if there are errors in python
If you are using the App Engine Launcher then by clicking on the Logs you can see all the logs and errors.
An alternative way is to start the development server via the command line (as it's already mentioned) and you will see all the logs there, which makes it much easier to work with because the Logs windows is not that flexible.
While using Google App Engine if there is an error in python the result is a blank page. It is difficult to debug python since you don't get line number on which there is error. It is extremely frustrating when you get blank page because of indentation error. Is there any way to execute python google app engine script in python interpreter so i get python error there itself.