Hi All, Do you guys on this lists have any ideas how packages can indicate to package managers like setuptools could indicate that if they are required by another package, that requirement must be for greater than a certain version? This stems from the "backwards compatibility" discussion for zope.interface here: https://mail.zope.org/pipermail/zope-dev/2009-November/038417.html Off the top of my head, zope.component could spell it's requirement as: def setup( ... incompatible_with='<4.0' ) Whereby, setuptools would raise an exception if the following packages were installed: def setup( ... install_requires=['zope.component'] ) def setup( ... install_requires=['zope.component >= 3.4.1'] ) ...while it wouldn't for the following package: def setup( ... install_requires=['zope.component >= 4'] ) Ideas? cheers, Chris -- Simplistix - Content Management, Batch Processing & Python Consulting - http://www.simplistix.co.uk