Indexing list of lists
hildegarde_roth at yahoo.de
Thu Sep 18 19:50:46 CEST 2003
> Like it or not, there are no "different dimensions", just lists of lists
> of lists...
You are being too litteral. A list of list is like a 2D array from an
indexing point of view, a list of lists of lists like a 3D array etc.
E.g., (((1,10),(2,20),(3,30)),((-1,'A'),(-2,'B'),(-3,'C'))) is a
2 x 3 x 2 rectangular data structure and has 3 dimensions. Hence,
e.g., l[0;2;1] ~ l = 30
> [alist, alist[-3], alist] and [alist[i] for i in [2, -3, 7]]
I agree that comprehensions alleviate the problem to an extent.
However the first notation is definitely cumbersome for all but the
shortest index lists.
> It covers the most common cases of list item extraction with a concise
1/ it is more or less redundant: the (x)range syntax could have been
extended with the same effect
2/ it lacks generality since it can only generate arithmetic progressions
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