Schwartzian transform for tuple in list

[Terry Reedy]

David Di Biase wrote:
> When you say slightly, is it enough to make a difference? Why would 
> getitems be faster even - not sure I can think why...
> 

Using key is faster than cmp because key is called just once for each 
item whereas cmp is called once for each of the O(nlogn) compares.

Operator.itemgetter is written in C and hence should be faster than a 
wrapper written in Python.