Chanelling Guido - dict subclasses

[John Ladasky]

On Wednesday, January 15, 2014 12:40:33 AM UTC-8, Peter Otten wrote:
> Personally I feel dirty whenever I write Python code that defeats duck-
> typing -- so I would not /recommend/ any isinstance() check.

While I am inclined to agree, I have yet to see a solution to the problem of flattening nested lists/tuples which avoids isinstance().  If anyone has written one, I would like to see it, and consider its merits.