Of course it's not really a mystery; a tremendous number of Apis only accept a file name. That's why it's there. And only something well connected to the importer system knows how and whether the extraction is needed.

Why is that the case? If the bytes are available, then whoever needs can write them to a temp file, pass that name, and clean up afterwards. Is managing a cache of arbitrary files extracted from zips is a mainstream use case which distlib needs to support? Regards, Vinay Sajip