astropy/astropy — pull request #1909 by nhmc (2013-12-15 23:17:53+00:00)
Title: Add an 'inverse' cosmology function

Following discussion on the list, here's an example implementation of an inverse function for the cosmology package.

Documentation and a changelog still needs to be added, but I thought I'd open this PR to get feedback on the approach. @aconley and @eteq might want to take a look.