Reading online zip files - zipfile and zlib, wbits

[Brendan]

I am fooling around with accessing contents of zip files online. I
download the tail end of the zip and use zipfile to get the zip
central directory structure. I download the section of the zip file I
need, directly read the zip file headers and use that information with
zlib to uncompress the data. The files I am examining will always be
compressed using deflate, with a wbits value of -15(minus for
headerless data because I am unsure whether the zip file header is
what zlib expects).

I can not find anywhere in the PK Zip Application notes (
http://www.pkware.com/documents/casestudies/APPNOTE.TXT ) how to
determine the value I should uze for wbits with zlib.decompress. I
have determined it is -15 from experimentation. Does anyone know the
answer to this?