Category "compression"

How can I estimate the compressibility of a file without compressing it?

I'm using an event loop based server in twisted python that stores files, and I'd like to be able to classify the files according to their compressibility. If

How to efficiently predict if data is compressible

I want to write a storage backend to store larger chunks of data. The data can be anything, but it is mainly binary files (images, pdfs, jar files) or text file