issues: 218277814

The following fails for 2.7 but not 3.5 (reproducible script at https://gist.github.com/89bd5bd62a475510b2611cbff8d5c67a): ```python In [1]: import xarray as xr

In [2]: import numpy as np

In [3]: da = xr.DataArray(np.random.rand(100,10), dims=['nCells','nVertLevels'])

In [4]: mask = xr.DataArray(np.zeros((100,), dtype='bool'), dims='nCells')

In [5]: da.where(mask, drop=True)

ValueError Traceback (most recent call last) <ipython-input-5-ca5cd9c083a9> in <module>() ----> 1 da.where(mask, drop=True)

/Users/pwolfram/src/xarray/xarray/core/common.pyc in where(self, cond, other, drop) 681 outcond = cond.isel(clip) 682 indexers = {dim: outcond.get_index(dim) for dim in outcond.dims} --> 683 outobj = self.sel(indexers) 684 else: 685 outobj = self

/Users/pwolfram/src/xarray/xarray/core/dataarray.pyc in sel(self, method, tolerance, drop, indexers) 670 self, indexers, method=method, tolerance=tolerance 671 ) --> 672 result = self.isel(drop=drop, pos_indexers) 673 return result._replace_indexes(new_indexes) 674

/Users/pwolfram/src/xarray/xarray/core/dataarray.pyc in isel(self, drop, indexers) 655 DataArray.sel 656 """ --> 657 ds = self._to_temp_dataset().isel(drop=drop, indexers) 658 return self._from_temp_dataset(ds) 659

/Users/pwolfram/src/xarray/xarray/core/dataset.pyc in isel(self, drop, indexers) 1115 for name, var in iteritems(self._variables): 1116 var_indexers = dict((k, v) for k, v in indexers if k in var.dims) -> 1117 new_var = var.isel(var_indexers) 1118 if not (drop and name in var_indexers): 1119 variables[name] = new_var

/Users/pwolfram/src/xarray/xarray/core/variable.pyc in isel(self, **indexers) 545 if dim in indexers: 546 key[i] = indexers[dim] --> 547 return self[tuple(key)] 548 549 def squeeze(self, dim=None):

/Users/pwolfram/src/xarray/xarray/core/variable.pyc in getitem(self, key) 375 dims = tuple(dim for k, dim in zip(key, self.dims) 376 if not isinstance(k, (int, np.integer))) --> 377 values = self._indexable_data[key] 378 # orthogonal indexing should ensure the dimensionality is consistent 379 if hasattr(values, 'ndim'):

/Users/pwolfram/src/xarray/xarray/core/indexing.pyc in getitem(self, key) 465 466 def getitem(self, key): --> 467 key = self._convert_key(key) 468 return self._ensure_ndarray(self.array[key]) 469

/Users/pwolfram/src/xarray/xarray/core/indexing.pyc in _convert_key(self, key) 452 if any(not isinstance(k, (int, np.integer, slice)) for k in key): 453 # key would trigger fancy indexing --> 454 key = orthogonal_indexer(key, self.shape) 455 return key 456

/Users/pwolfram/src/xarray/xarray/core/indexing.pyc in orthogonal_indexer(key, shape) 77 """ 78 # replace Ellipsis objects with slices ---> 79 key = list(canonicalize_indexer(key, len(shape))) 80 # replace 1d arrays and slices with broadcast compatible arrays 81 # note: we treat integers separately (instead of turning them into 1d

/Users/pwolfram/src/xarray/xarray/core/indexing.pyc in canonicalize_indexer(key, ndim) 65 return indexer 66 ---> 67 return tuple(canonicalize(k) for k in expanded_indexer(key, ndim)) 68 69

/Users/pwolfram/src/xarray/xarray/core/indexing.pyc in <genexpr>((k,)) 65 return indexer 66 ---> 67 return tuple(canonicalize(k) for k in expanded_indexer(key, ndim)) 68 69

/Users/pwolfram/src/xarray/xarray/core/indexing.pyc in canonicalize(indexer) 62 'array indexing; all subkeys must be ' 63 'slices, integers or sequences of ' ---> 64 'integers or Booleans' % indexer) 65 return indexer 66

ValueError: invalid subkey array([], dtype=object) for integer based array indexing; all subkeys must be slices, integers or sequences of integers or Booleans ```