a query on sorting

[Gabriel Genellina]

At Wednesday 27/9/2006 08:51, Steve Holden wrote:

>If you want the indexes as well you need to become a bit tricky.
>Remember that enumerate() will produced two-element tuples with the
>index value associated with the list value.
>
>   >>> [x for x in enumerate(a)]
>[(0, 9), (1, 4), (2, 3), (3, 5), (4, 2), (5, 6), (6, 7), (7, 1), (8, 2)]
>
>But you really want the index second, so the sort works on the list
>values not the index values. Combining all this we get
>
>   >>> sorted((x[1], x[0]) for x in enumerate(a))
>[(1, 7), (2, 4), (2, 8), (3, 2), (4, 1), (5, 3), (6, 5), (7, 6), (9, 0)]

Why forcing to use enumerate if it doesn't fit? And a generator won't 
help here since you have to access all the items.

sorted([(a[i],i) for i in range(len(a))])

If you want the ordered results and the indices exactly like in the 
matlab example:

 > [y,i] = sort(x);
y, i = zip(*sorted([(a[i],i) for i in range(len(a))]))



Gabriel Genellina
Softlab SRL 


	
	
		
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