title: How to modify EXIF data in python
body: <p>I am trying to edit/modify existing metadata within python 2.7. More specifically I have GPS coordinates in a my metedata, however the altitude field is incorrect. Is there a way of changing this?</p>
  <p>I have had a look at <code>PIL</code> <code>piexif</code> <code>pyexif</code>, but I cannot seem to find a way to modify existing fields.</p>
  <p>Has anyone managed to do this? It sounds like it would be very simple, but I can't seem to work it out.</p>