how to convert code that uses cmp to python3

[Mark Lawrence]

On 07/04/2016 21:56, Antoon Pardon wrote:
> Op 07-04-16 om 14:22 schreef Chris Angelico:
>
> ...
>
>> There's no __cmp__ method, but you could easily craft your own
>> compare() function:
>>
>> def compare(x, y):
>>      """Return a number < 0 if x < y, or > 0 if x > y"""
>>      if x == y: return 0
>>      return -1 if keyify(x) < keyify(y) else 1
>>
>> I'm not sure how your tree is crafted and how your "cheap" and
>> "expensive" comparisons previously worked, but give something like
>> this a try. I think you'll find it adequate.
>
> That solution will mean I will have to do about 100% more comparisons
> than previously.
>
> Lets simplify for the moment and suppose all keys are tuples of
> integers. Now because how trees are organised, the lower you
> descend in the tree, the closer the keys are together. In the
> case of tuples that means higher probability you have to traverse
> the two tuples further in order to find out which is greater.
>
> With the __cmp__ method, you only had to traverse the two tuples
> once in order to find out whether they were equal or if not which
> is the smaller and which is the greater.
>
> With this method I have to traverse the two tuples almost always
> twice. Once to find out if they are equal and if not a second
> time to find out which is greater.
>

Have you read this https://wiki.python.org/moin/HowTo/Sorting ?

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence