[Python-ideas] Possible new slice behaviour? Was ( Negative slice discussion.)

[Ron Adam]

On 11/05/2013 05:02 AM, Nick Coghlan wrote:
>  > Are there plans for pythons builtin types to use multidimensional indexing?
>
> Yes, memoryview already has some support for multidimensional array shapes,
> and that's likely to be enhanced further in 3.5.

Ok,  I suppose other builtin types may (or may not) follow that pattern.

But in this light, I agree, it's best not to create a more complex pattern 
to handle for those cases.

(... and it worked so nicely,  Oh Well.)


The alternative is to have a function that does what the slice syntax does. 
  And then extend that.  It seems to me it's a good idea to have function 
equivalents of syntax when possible in any case.

        do_slice(obj, slices, *callables)

Where slices is either a single slice or a tuple of slices or indices.

# Examples

class GetSlice:
     """Return a slices from slice syntax."""
     def __getitem__(self, slc):
         return slc

gs = GetSlice()

seq = list(range(10))

print(do_slice(seq, gs[1, 5, 7]))
print(do_slice(seq, gs[3:7], openi))
print(do_slice(seq, gs[3:7], closedi))
print(do_slice(seq, gs[3:7], closedi, onei))
print(do_slice(seq, gs[3:5, 7:8, 9], reversei))
print(do_slice(seq, gs[:], reversei))
print(do_slice(seq, range(-5, 15), wrapi))
print(do_slice(seq, range(15, -5, -1), wrapi))
"""
[1, 5, 7]
[4, 5, 6]
[3, 4, 5, 6, 7]
[2, 3, 4, 5, 6]
[[4, 3], [7], 9]
[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
[5, 6, 7, 8, 9, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, 3, 4]
[5, 4, 3, 2, 1, 0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 9, 8, 7, 6]
"""


Cheers,
    Ron