Q: How to empty Google App Engine's local database Where do I go to delete everything in my local db? 
I saw this: http://fourtyten.blogspot.com/2009/07/how-to-empty-google-app-engines-local.html
But my WEB-INF directory doesn't have a local_db.bin
I saw this post also How to delete all datastore in Google App Engine?

If you're talking about the development datastore, you'll just have to delete the following file: "./WEB-INF/appengine-generated/local_db.bin". The file will be generated for you again next time you run the development server and you'll have a clear db.

But I can't find this folder either. 
--Update---
I found this post How do I delete all entities from my local Google App-engine datastore? and it looks like I can use dev_appserver.py --clear_datastore dennys
But when I run that I get this python dev_appserver.py --celar_datastore dennys
python: can't open file 'dev_appserver.py': [Errno 2] No such file or directory

How do I find where dev_appserver.py is on my machine?

A: To delete data follow the steps here: http://code.google.com/appengine/docs/python/tools/devserver.html#Using_the_Datastore
This question is not longer valid, my problem is listed here: AppConfigNotFoundError for dev_appserver.py on Django-nonrel and Google App Engine

A: Open up a terminal and execute the following
cd /
find . -iname "*dev_appserver.py*" -type f

then add that to your path in your .bash_profile as so
PATH=$PATH:<directory from previous command>

then use the dev_appserver.py as you had previously mentioned like so
dev_appserver.py --clear_datastore=yes <your app's directory>

Keep in mind that python dev_appserver.py <your_app> might not work
