#! code

I have talked about swapping values without a temporary third variable before, but there is another way to do this which doesn't make the code unreadable. This is by using the list() function in the following way.

If you allow users to upload data to your site you might have a situation where a data directory might be full of temporary files. In the long term you will want to get rid of these files as they have served their purpose and are no longer needed.