Empty Series[datetime64[ns, tz]].reindex fails

[TomAugspurger]

TZ-naive is fine.

In [41]: pd.Series(dtype='datetime64[ns]').reindex([0, 1])
Out[41]:
0   NaT
1   NaT
dtype: datetime64[ns]

In [42]: pd.Series(dtype='datetime64[ns, UTC]').reindex([0, 1])

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-42-a882503115f7> in <module>()
----> 1 pd.Series(dtype='datetime64[ns, UTC]').reindex([0, 1])

~/sandbox/pandas/pandas/core/series.py in reindex(self, index, **kwargs)
   3309     @Appender(generic._shared_docs['reindex'] % _shared_doc_kwargs)
   3310     def reindex(self, index=None, **kwargs):
-> 3311         return super(Series, self).reindex(index=index, **kwargs)
   3312
   3313     def drop(self, labels=None, axis=0, index=None, columns=None,

~/sandbox/pandas/pandas/core/generic.py in reindex(self, *args, **kwargs)
   3691         # perform the reindex on the axes
   3692         return self._reindex_axes(axes, level, limit, tolerance, method,
-> 3693                                   fill_value, copy).__finalize__(self)
   3694
   3695     def _reindex_axes(self, axes, level, limit, tolerance, method, fill_value,

~/sandbox/pandas/pandas/core/generic.py in _reindex_axes(self, axes, level, limit, tolerance, method, fill_value, copy)
   3709             obj = obj._reindex_with_indexers({axis: [new_index, indexer]},
   3710                                              fill_value=fill_value,
-> 3711                                              copy=copy, allow_dups=False)
   3712
   3713         return obj

~/sandbox/pandas/pandas/core/generic.py in _reindex_with_indexers(self, reindexers, fill_value, copy, allow_dups)
   3812                                                 fill_value=fill_value,
   3813                                                 allow_dups=allow_dups,
-> 3814                                                 copy=copy)
   3815
   3816         if copy and new_data is self._data:

~/sandbox/pandas/pandas/core/internals.py in reindex_indexer(self, new_axis, indexer, axis, fill_value, allow_dups, copy)
   4419         if axis == 0:
   4420             new_blocks = self._slice_take_blocks_ax0(indexer,
-> 4421                                                      fill_tuple=(fill_value,))
   4422         else:
   4423             new_blocks = [blk.take_nd(indexer, axis=axis, fill_tuple=(

~/sandbox/pandas/pandas/core/internals.py in _slice_take_blocks_ax0(self, slice_or_indexer, fill_tuple)
   4458                 return [blk.take_nd(slobj, axis=0,
   4459                                     new_mgr_locs=slice(0, sllen),
-> 4460                                     fill_tuple=fill_tuple)]
   4461
   4462         if sl_type in ('slice', 'mask'):

~/sandbox/pandas/pandas/core/internals.py in take_nd(self, indexer, axis, new_mgr_locs, fill_tuple)
   1256             fill_value = fill_tuple[0]
   1257             new_values = algos.take_nd(values, indexer, axis=axis,
-> 1258                                        allow_fill=True, fill_value=fill_value)
   1259
   1260         if new_mgr_locs is None:

~/sandbox/pandas/pandas/core/algorithms.py in take_nd(arr, indexer, axis, out, fill_value, mask_info, allow_fill)
   1580         return arr.take(indexer, fill_value=fill_value, allow_fill=allow_fill)
   1581     elif is_datetimetz(arr):
-> 1582         return arr.take(indexer, fill_value=fill_value, allow_fill=allow_fill)
   1583     elif is_interval_dtype(arr):
   1584         return arr.take(indexer, fill_value=fill_value, allow_fill=allow_fill)

~/sandbox/pandas/pandas/core/indexes/datetimelike.py in take(self, indices, axis, allow_fill, fill_value, **kwargs)
    497                                            allow_fill=allow_fill,
    498                                            fill_value=fill_value,
--> 499                                            na_value=iNaT)
    500
    501         # keep freq in PeriodIndex, reset otherwise

~/sandbox/pandas/pandas/core/indexes/base.py in _assert_take_fillable(self, values, indices, allow_fill, fill_value, na_value)
   2178                        'all indices must be >= -1')
   2179                 raise ValueError(msg)
-> 2180             taken = values.take(indices)
   2181             mask = indices == -1
   2182             if mask.any():

IndexError: cannot do a non-empty take from an empty axes.

[WillAyd]

IIUC datetime64 has a customized algos take helper that accounts for NA values. datetime64-tz does not have this and ends up hitting the code linked below in base (bottom of your traceback):

pandas/pandas/core/indexes/base.py

Line 2180 in c8fcfcb

taken = values.take(indices)

I suppose an easy fix is to resize values to match the size of indices if the former is empty but the latter is not. Not sure what edge cases might fall in between.

Happy to submit a PR if you think it's a good approach

[sschuldenzucker]

This seems to be fixed in 0.23.1. The above code now doesn't crash, but yields

0   NaT
1   NaT
dtype: datetime64[ns, UTC]

as expected.

Btw, I got here because I saw a crash in 0.20.1 in the same source line mentioned above when trying to print (format) an all-NaT categorical datetime series. This is fixed in 0.23.1, too.

[WillAyd]

Thanks @sschuldenzucker - this may have been fixed via some of the work @jbrockmendel has been doing. If you are looking to make a contribution then we'll gladly accept a test to ensure this doesn't break in the future