How can I protect my AWS access id and secret key in my python application
Don't put it in applications you plan to distribute.  It'll be visible and they can launch instances that are directly billable to you or worst..they can take down instances if you use it in production.
I would look at your programs design and seriously question why I need to include that information in the app.  If you post more details on the design I'm sure we can help you figure out a way in which you don't need to bundle this information.
I'm making an application in Python and using Amazon Web Services in some modules.
I'm now hard coding my AWS access id and secret key in *.py file. Or might move them out to an configuration file in future.
But there's a problem, how can I protect AWS information form other people? As I know python is a language that easy to de-compile. 
Is there a way to do this? 

Well what I'm making is an app to help user upload/download stuff from cloud. I'm using Amazon S3 as cloud storage. As I know Dropbox also using S3 so I'm wondering how they protects the key.

After a day's research I found something.
I'm now using boto (an AWS library for python). I can use a function of 'generate_url(X)' to get a url for the app to accessing the object in S3. The url will be expired in X seconds.
So I can build a web service for my apps to provide them the urls. The AWS keys will not be set into the app but into the web service.
It sounds great, but so far I only can download objects with this function, upload doesn't work. Any body knows how to use it for uploading?

Does anyone here know how to use key.generate_url() of boto to get a temporary url for uploading stuff to S3?