Hi Steve You wrote that we don't need a seq.slice(a, b) method, because the existing syntax does the job fine.
To change the subject slightly, it seems to me that we don't need both seq[a:b] and slice(a, b). Certainly, we can get by without either. If we didn't have seq[a:b] we could use slice(a, b) instead: >>> lst[10:20] [10, 11, 12, 13, 14, 15, 16, 17, 18, 19] >>> lst[slice(10, 20)] [10, 11, 12, 13, 14, 15, 16, 17, 18, 19] And if we have seq[a:b] then we can get our hands on slice(a, b): >>> class GetItemArg: ... def __getitem__(self, arg): ... return arg >>> getslice = GetItemArg() >>> getslice[10:20] slice(10, 20, None) A purist might say that seq[a:b] is syntactic sugar for seq[slice(a,b)]. And that it is yet another use of the colon. However, I do find it convenient and familiar. So I'd like to keep it, and will defend it against purists who wish to remove it. In that, Steve and I (and I think the original poster) agree. I don't think I'd get the same benefit for seq.slice(a, b) being added to the methods of the built-in sequence types (such as list). But I'd prefer that the decision would be on pragmatic grounds, based on experience. I certainly think the meaning of seq.slice(a, b) is clear, and would more easily discovered than the seq[a:b] notation. Certainly, neither 'slice' nor ':' appear in >>> help(list) A personal interest aside: A list is one-dimensional. Numpy deals with multi-dimensional rectangular arrays of numbers. In my mathematics area, I deal with triangles of numbers (think Pascal's Triangle), and also pyramids of numbers. (aside continued). Numpy allows 'slicing' and reshaping of its rectangular arrays. In my mathematics area, I'd like to similarly be able to slice triangles and pyramids of numbers. For example, the central binomial coefficients: http://oeis.org/A000984 Finally, off-topic, I find it a bit odd that in the below we get syntax errors (rather than a run-time error). >>> getslice[] SyntaxError: invalid syntax >>> getslice[1:2] slice(1, 2, None) >>> getslice[1:2:3] slice(1, 2, 3) >>> getslice[1:2:3:4] SyntaxError: invalid syntax -- Jonathan
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