Make _holder a property for all

pandas-dev · TomAugspurger · Feb 2, 2018 · Jan 15, 2018 · Jan 18, 2018 · Jan 18, 2018
commit cd0997e354121bc0414ef1675cb5b8241944a9b0
diff --git a/pandas/core/internals.py b/pandas/core/internals.py
@@ -64,6 +64,7 @@
 from pandas.core.indexing import maybe_convert_indices, length_of_indexer
 from pandas.core.arrays import Categorical
 from pandas.core.indexes.datetimes import DatetimeIndex
+from pandas.core.indexes.timedeltas import TimedeltaIndex
 from pandas.io.formats.printing import pprint_thing
 
 import pandas.core.missing as missing
@@ -104,7 +105,6 @@ class Block(PandasObject):
     _verify_integrity = True
     _validate_ndim = True
     _ftype = 'dense'
-    _holder = None
     _concatenator = staticmethod(np.concatenate)

     def __init__(self, values, placement, ndim=None):
@@ -135,6 +135,15 @@ def _maybe_validate_ndim(self, values, ndim):
         if self._validate_ndim and values.ndim != ndim:
             raise ValueError('Wrong number of dimensions')
 
+    @property
+    def _holder(self):
+        """The array-like that can hold the underlying values.
+
+        None for 'Block', overridden by subclasses that don't
+        use an ndarray.
+        """
+        return None
+
     @property
     def _consolidate_key(self):
         return (self._can_consolidate, self.dtype.name)
@@ -1689,7 +1698,6 @@ class NonConsolidatableMixIn(object):
     _can_consolidate = False
     _verify_integrity = False
     _validate_ndim = False
-    _holder = None
 
     def __init__(self, values, placement, ndim=None):
         """Initialize a non-consolidatable block.
@@ -1832,8 +1840,7 @@ class ExtensionBlock(NonConsolidatableMixIn, Block):
     """
     @property
     def _holder(self):
-        # For extension blocks, the holder is values-dependent so we
-        # use a property.
+        # For extension blocks, the holder is values-dependent.
         return type(self.values)
 
     @property
@@ -2012,6 +2019,11 @@ def should_store(self, value):
 
 
 class DatetimeLikeBlockMixin(object):
+    """Mixin class for DatetimeBlock and DatetimeTZBlock."""
+
+    @property
+    def _holder(self):
+        return DatetimeIndex
 
     @property
     def _na_value(self):
@@ -2044,6 +2056,10 @@ def __init__(self, values, placement, ndim=None):
         super(TimeDeltaBlock, self).__init__(values,
                                              placement=placement, ndim=ndim)
 
+    @property
+    def _holder(self):
+        return TimedeltaIndex
+
     @property
     def _box_func(self):
         return lambda x: tslib.Timedelta(x, unit='ns')
@@ -2424,7 +2440,6 @@ class CategoricalBlock(ExtensionBlock):
     is_categorical = True
     _verify_integrity = True
     _can_hold_na = True
-    _holder = Categorical
     _concatenator = staticmethod(_concat._concat_categorical)
 
     def __init__(self, values, placement, ndim=None):
@@ -2435,6 +2450,10 @@ def __init__(self, values, placement, ndim=None):
                                                placement=placement,
                                                ndim=ndim)
 
+    @property
+    def _holder(self):
+        return Categorical
+
     @property
     def array_dtype(self):
         """ the dtype to return if I want to construct this block as an
@@ -2673,7 +2692,6 @@ def set(self, locs, values, check=False):
 class DatetimeTZBlock(NonConsolidatableMixIn, DatetimeBlock):
     """ implement a datetime64 block with a tz attribute """
     __slots__ = ()
-    _holder = DatetimeIndex
     _concatenator = staticmethod(_concat._concat_datetime)
     is_datetimetz = True
 
@@ -2856,7 +2874,6 @@ class SparseBlock(NonConsolidatableMixIn, Block):
     _box_to_block_values = False
     _can_hold_na = True
     _ftype = 'sparse'
-    _holder = SparseArray
     _concatenator = staticmethod(_concat._concat_sparse)
 
     def __init__(self, values, placement, ndim=None):
@@ -2866,6 +2883,10 @@ def __init__(self, values, placement, ndim=None):
         assert isinstance(values, SparseArray)
         super(SparseBlock, self).__init__(values, placement, ndim=ndim)
 
+    @property
+    def _holder(self):
+        return SparseArray
+
     @property
     def shape(self):
         return (len(self.mgr_locs), self.sp_index.length)

diff --git a/pandas/tests/internals/test_internals.py b/pandas/tests/internals/test_internals.py
@@ -11,7 +11,7 @@
 from distutils.version import LooseVersion
 import itertools
 from pandas import (Index, MultiIndex, DataFrame, DatetimeIndex,
-                    Series, Categorical)
+                    Series, Categorical, TimedeltaIndex, SparseArray)
 from pandas.compat import OrderedDict, lrange
 from pandas.core.sparse.array import SparseArray
 from pandas.core.internals import (BlockPlacement, SingleBlockManager,
@@ -1263,6 +1263,18 @@ def test_binop_other(self, op, value, dtype):
         assert_series_equal(result, expected)
 
 
+@pytest.mark.parametrize('typestr, holder', [
+    ('category', Categorical),
+    ('M8[ns]', DatetimeIndex),
+    ('M8[ns, US/Central]', DatetimeIndex),
+    ('m8[ns]', TimedeltaIndex),
+    ('sparse', SparseArray),
+])
+def test_holder(typestr, holder):
+    blk = create_block(typestr, [1])
+    assert blk._holder is holder
+
+
 def test_deprecated_fastpath():
     # GH#19265
     values = np.random.rand(3, 3)