Is there a Python module that already does this?

[David Eppstein]

Here it is in a functional programming style:

import operator

def flatten(x):
        if operator.isSequenceType(x) and (len(x) != 1 or x[0] != x):
                return reduce(operator.concat, map(flatten, x), [])
        else:
                return [x]
                
print flatten(["cat",5,['dog',[3,3,1]],"zoo"])

...outputs...
['c', 'a', 't', 5, 'd', 'o', 'g', 3, 3, 1, 'z', 'o', 'o']

All that list copying makes it somewhat inefficient, though...
-- 
David Eppstein       UC Irvine Dept. of Information & Computer Science
eppstein at ics.uci.edu http://www.ics.uci.edu/~eppstein/