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ensure rename does not change index type #3532

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Nov 15, 2019
Merged

ensure rename does not change index type #3532

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3e3f5ec
ensure rename does not change index type
mathause Nov 14, 2019
5064cd2
test requires cftime
mathause Nov 14, 2019
3b85495
test orig.indexes[time].name is conserved
mathause Nov 15, 2019
ec76154
use index.rename()
mathause Nov 15, 2019
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4 changes: 4 additions & 0 deletions doc/whats-new.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,10 @@ New Features

Bug fixes
~~~~~~~~~
- Ensure an index of type ``CFTimeIndex`` is not converted to a ``DatetimeIndex`` when
calling :py:meth:`Dataset.rename` (also :py:meth:`Dataset.rename_dims`
and :py:meth:`xr.Dataset.rename_vars`). By `Mathias Hauser <https://github.com/mathause>`_
(:issue:`3522`).
- Fix a bug in `set_index` in case that an existing dimension becomes a level variable of MultiIndex. (:pull:`3520`)
By `Keisuke Fujii <https://github.com/fujiisoup>`_.
- Harmonize `_FillValue`, `missing_value` during encoding and decoding steps. (:pull:`3502`)
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3 changes: 2 additions & 1 deletion xarray/core/dataset.py
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Expand Up @@ -2667,7 +2667,8 @@ def _rename_indexes(self, name_dict, dims_set):
verify_integrity=False,
)
else:
index = pd.Index(v, name=new_name)
index = v
index.name = new_name
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@mathause mathause Nov 14, 2019 •
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Alternatively there is a index = v._shallow_copy(name=new_name) method. It is "an internal non-public method" in pandas. Should I use it anyway?

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While I think it's fairly stable, you're right—best practice is indeed to avoid.

I think the current code will mutate the existing index name, is that correct? We should at least test to ensure that doesn't happen. I think .rename rather than direct assignment will avoid this (and calls _shallow_copy from within pandas so we're safe)

FWIW I think we can replace https://github.com/pydata/xarray/pull/3532/files#diff-921db548d18a549f6381818ed08298c9R2662-R2667 also with .rename, but it's minor and doesn't need to be in this PR

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Oh, there is even rename - I did not see that, will switch to it.

indexes[new_name] = index
return indexes

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25 changes: 25 additions & 0 deletions xarray/tests/test_dataset.py
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Expand Up @@ -8,6 +8,7 @@
import numpy as np
import pandas as pd
import pytest
from pandas.core.indexes.datetimes import DatetimeIndex

import xarray as xr
from xarray import (
Expand All @@ -22,6 +23,7 @@
open_dataset,
set_options,
)
from xarray.coding.cftimeindex import CFTimeIndex
from xarray.core import dtypes, indexing, utils
from xarray.core.common import duck_array_ops, full_like
from xarray.core.npcompat import IS_NEP18_ACTIVE
Expand Down Expand Up @@ -2458,6 +2460,29 @@ def test_rename_vars(self):
with pytest.raises(ValueError):
original.rename_vars(names_dict_bad)

def test_rename_does_not_change_index_type(self):
# make sure CFTimeIndex is not converted to DatetimeIndex #3522

time = xr.cftime_range(start="2000", periods=6, freq="2MS", calendar="noleap")

ds = Dataset(coords={"time": time})

# make sure renaming does not change the type of the index
assert isinstance(ds.indexes["time"], CFTimeIndex)
assert isinstance(ds.rename().indexes["time"], CFTimeIndex)
assert isinstance(ds.rename_dims().indexes["time"], CFTimeIndex)
assert isinstance(ds.rename_vars().indexes["time"], CFTimeIndex)

time = pd.date_range(start="2000", periods=6, freq="2MS")

ds = Dataset(coords={"time": time})

# make sure renaming does not change the type of the index
assert isinstance(ds.indexes["time"], DatetimeIndex)
assert isinstance(ds.rename().indexes["time"], DatetimeIndex)
assert isinstance(ds.rename_dims().indexes["time"], DatetimeIndex)
assert isinstance(ds.rename_vars().indexes["time"], DatetimeIndex)

def test_swap_dims(self):
original = Dataset({"x": [1, 2, 3], "y": ("x", list("abc")), "z": 42})
expected = Dataset({"z": 42}, {"x": ("y", [1, 2, 3]), "y": list("abc")})
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