While stack:

[Corey Richardson]

On Fri, 1 Jun 2012 18:59:57 +0100 (BST)
David Shi <davidgshi at yahoo.co.uk> <davidgshi at yahoo.co.uk> wrote:

> Can any one clarify what "while stack:" mean?
> 
> Regards,
> 
> David
> 

Formal explanation:
http://docs.python.org/reference/compound_stmts.html#while

Informal introduction:
http://learnpythonthehardway.org/book/ex33.html

Simplistic summary: it executes the indented code under the "while"
until stack evaluates to non-True.

-- 
Corey Richardson