I have 2 egg versions of 'mypkg' installed in /custom/site-packages, 0.0.1 and 0.0.2 This directory is an alternate site directory as described here: http://peak.telecommunity.com/DevCenter/EasyInstall#administrator-installati... I have elected to not use easy_install --multi-version since it's convenient to have easy-install.pth set up so that users can by default import the latest version if they don't explicitly require a version either via setup.py or by using pkg_resources.require directly. However, require() is refusing to resolve version 0.0.1: Python 2.6.2 (r262:71600, Jul 16 2009, 14:04:28) [GCC 4.1.2 20071124 (Red Hat 4.1.2-42)] on linux2 Type "help", "copyright", "credits" or "license" for more information. py> from pkg_resources import require py> require("mypkg==0.0.1") Traceback (most recent call last): File "<stdin>", line 1, in <module> File "build/bdist.linux-x86_64/egg/pkg_resources.py", line 626, in require File "build/bdist.linux-x86_64/egg/pkg_resources.py", line 528, in resolve pkg_resources.VersionConflict: (mypkg 0.0.2 (/custom/site-packages/ mypkgl-0.0.2-py2.6.egg), Requirement.parse('mypkg==0.0.1')) py> Can someone explain what exactly the conflict is (I'm guessing pkg_resources is unhappy that 0.0.2 is already on sys.path)? I'd like for users to be able to explicitly use the older version if they're not yet comfortable with the new one. And a user just writing a simple script without wanting setuptools, or even simply trying something in the interactive interpreter, should be able to access the latest version without needing to know about pkg_resources.