[Tutor] Sorting list of tuples in two passes

[Steven D'Aprano]

Dayo Adewunmi wrote:

> It works when I use your example, but I don't understand why it won't 
> work when I use 4-element tuples instead of 2:

What makes you say it doesn't work? It looks like it works to me:

>  >>>l = [('wascas','aaa','fdvdfv', 1), ('rtgdsf','bbb','trfg', 1), 
> ('addwe','ccc','esd', 1), ('xasd','aaa','wascaq', 2), 
> ('nhy','bbb','asw', 2), ('zzzz','ccc','dgdeg', 2)]
>  >>> l
> [('wascas', 'aaa', 'fdvdfv', 1), ('rtgdsf', 'bbb', 'trfg', 1), ('addwe', 
> 'ccc', 'esd', 1), ('xasd', 'aaa', 'wascaq', 2), ('nhy', 'bbb', 'asw', 
> 2), ('zzzz', 'ccc', 'dgdeg', 2)]
>  >>> l.sort(key=itemgetter(3))
>  >>> l
> [('wascas', 'aaa', 'fdvdfv', 1), ('rtgdsf', 'bbb', 'trfg', 1), ('addwe', 
> 'ccc', 'esd', 1), ('xasd', 'aaa', 'wascaq', 2), ('nhy', 'bbb', 'asw', 
> 2), ('zzzz', 'ccc', 'dgdeg', 2)]

List "l" is now sorted by the element in position 3 (counting from zero, 
not one): 1 1 1 2 2 2


>  >>> l.sort(key=itemgetter(1))
>  >>> l
> [('wascas', 'aaa', 'fdvdfv', 1), ('xasd', 'aaa', 'wasca    q', 2), 
> ('rtgdsf', 'bbb', 'trfg', 1), ('nhy', 'bbb', '
> asw', 2), ('addwe', 'ccc', 'esd', 1), ('zzzz', 'ccc', 'dgdeg', 2)]

And now elements are sorted in order of position 1:
aaa aaa bbb bbb ccc ccc

In the event of ties (and there are three pairs of ties) the elements 
keep the relative order they were in after the first sort.

The sorting worked just as expected.




-- 
Steven