title: Library to perform coordinate system transformations?
body: <p>Is there a python library which handles coordinate system transformations?
  I'm working with numpy meshgrids, but sometimes it's useful to switch the coordinate systems.
  Since I don't want to reinvent the wheel, are there any libraries which handle:</p>
  
  <ul>
  <li>transformations (cartesian, spherical, polar, ...)</li>
  <li>translations </li>
  <li>rotations?</li>
  </ul>