It is possible and supported but not very elegant since the marker syntax can only compare versions as strings (you wouldn't want to use < and have the wrong dependencies under Python 2.7.10). One solution would be to check that you are not running on any of the older releases of Python 2.7, like so: In setup.py: extras_require={ ':python_version == "2.7" and (python_full_version!="2.7.8" and python_full_version!="2.7.7" and ...)': ['backports.ssl_match_hostname'], } This means the extra named '' a.k.a. the default dependencies includes your package, but only if the expression after the colon : evaluates to True. bdist_wheel preserves the expression in .whl binary packages. On Fri, Dec 12, 2014 at 11:09 AM, Ben Darnell <ben@bendarnell.com> wrote:

Hi distutils-sig,

Tornado depends on backports.ssl_match_hostname on python 2, but this is no longer needed with (cpython) 2.7.9. We have a PR to make this dependency conditional on the minor version of python (https://github.com/tornadoweb/tornado/pull/1276/files). We could also make the test something like `hasattr(ssl, 'SSLContext')`, which would be more compatible with pypy and other implementations, but the fundamental issues remain. Is it a good idea to distribute packages that will install different dependencies on different minor versions of python? Is it even possible with binary distributions? I'm thinking it's probably best to just live with the unused extra dependency (until we can completely drop support for python versions without modern ssl libraries), but I wanted to check and see if there is a clean way to deal with this.

Thanks, -Ben

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