Schwartzian transform for tuple in list

David Di Biase dave.dibiase at gmail.com
Wed Sep 24 23:02:33 CEST 2008


Hi,

I have a rather large list structure with tuples contained in them (it's
part of a specification I received) looks like so:
[(x1,y1,r1,d1),(x2,y2,r2,d2)...]

The list can range from about 800-1500 tuples in size and I'm currently
sorting it with this:

a_list.sort(lambda a, b: cmp(b[3], a[3]))

I'm actually sorting it by the last value in the tuple (d2). I have been
researching more efficient sorting algorithms and came across Schwartzian
transform via these links:

   -
   http://www.biais.org/blog/index.php/2007/01/28/23-python-sorting-efficiency
   -
   http://dev.fyicenter.com/Interview-Questions/Python/Can_you_do_a_Schwartzian_Transform_in_Python_.html

I get what's happening (sorta...errr...lol)  but I'm not sure if it is more
efficient in my scenario, if it is then I have no idea how to implement it
properly :-/

Would be great if a true expert would offer a suggestion for me...

Thanks!

David
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