AST is an Abstract Syntax Tree, which is built from Python source to analyze the latter without executing.

AST can be used to:

 * build dot graph - http://bugs.python.org/issue10399
 * 

See the talk [[http://blip.tv/pycon-us-videos-2009-2010-2011/pycon-2011-what-would-you-do-with-an-ast-4898264|What would you do with an AST]] by Matthew J Desmarais for more examples.