astor is designed to allow easy manipulation of Python source via the AST. There
are some other similar libraries, but astor focuses on the following areas:

 * Round-trip back to Python via Armin Ronacher's codegen.py module:
   ** Modified AST doesn't need linenumbers, ctx, etc. or otherwise be directly
      compileable
   ** Easy to read generated code as, well, code
 * Dump pretty-printing of AST
   ** Harder to read than round-tripped code, but more accurate to figure out
      what is going on.
   ** Easier to read than dump from built-in AST module
 * Non-recursive treewalk
   ** Sometimes you want a recursive treewalk (and astor supports that, starting
      at any node on the tree), but sometimes you don't need to do that. astor
      doesn't require you to explicitly visit sub-nodes unless you want to:
   ** You can add code that executes before a node's children are visited,
      and/or
   ** You can add code that executes after a node's children are visited, and/or
   ** You can add code that executes and keeps the node's children from being
      visited (and optionally visit them yourself via a recursive call)
   ** Write functions to access the tree based on object names and/or attribute
      names
   ** Enjoy easy access to parent node(s) for tree rewriting