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Fix RangeIndex slicing #10471

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Fix RangeIndex slicing #10471

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@benbovy benbovy commented Jun 30, 2025

dcherian
dcherian reviewed Jun 30, 2025
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xarray/indexes/range_index.py
@@ -84,9 +84,9 @@ def slice(self, sl: slice) -> "RangeCoordinateTransform":
# TODO: support reverse transform (i.e., start > stop)?
assert sl.start < sl.stop

new_size = (sl.stop - sl.start) // sl.step
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@dcherian dcherian Jun 30, 2025 •
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One trick I have learned is to use range objects to outsource this logic to CPython (e.g. #7586)

So you could do:

newrange = range(self.size)[sl]
start = newrange.start
step = newrange.step or 1
size = len(newrange)

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Nice trick, this also allows supporting reverse indexing without additional effort.

@benbovy
slicing impl: rely on range
ea6742c 
This also enables support for reverse slicing (added tests)
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slicing DataArray with RangeIndex coordinate can put coordinate in inconsistent state
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