Is there a Python module that already does this?

[David Eppstein]

In article <a3rbad$19u08k$1 at ID-98166.news.dfncis.de>, "MDK" <mdk at mdk.com> 
wrote:

> For example:
> 
> ("cat",5,['dog',[3,3,1]],"zoo")
> 
> Would become:
> 
> ('c','a','t',5,'d','o','g',3,3,1,'z','o','o')

This is standard in LISP as "flatten". Here's an implementation using 
simple generators.

from __future__ import generators

def flatten(x):
        def flatgen(x):
                try:
                        xg = iter(x)
                        for y in xg:
                                if y == x:
                                        # prevent infinite recursion
                                        # when x is a character
                                        yield x
                                        return
                                yg = flatgen(y)
                                for z in yg:
                                        yield z
                except TypeError:
                        yield x
        
        return tuple(flatgen(x))

print flatten(("cat",5,['dog',[3,3,1]],"zoo"))
('c', 'a', 't', 5, 'd', 'o', 'g', 3, 3, 1, 'z', 'o', 'o')
-- 
David Eppstein       UC Irvine Dept. of Information & Computer Science
eppstein at ics.uci.edu http://www.ics.uci.edu/~eppstein/