Create a common code path for 1d Frames

python/cudf/cudf/core/dataframe.py

@@ -10,7 +10,7 @@
 import warnings
 from collections import defaultdict
 from collections.abc import Iterable, Sequence
-from typing import Any, Optional, Set, TypeVar
+from typing import Any, Optional, TypeVar
 
 import cupy
 import numpy as np
@@ -554,6 +554,7 @@ def _align_input_series_indices(data, index):
 
         return data, index
 
+    # The `constructor*` properties are used by `dask` (and `dask_cudf`)
     @property
     def _constructor(self):
         return DataFrame
@@ -1456,7 +1457,7 @@ def _get_columns_by_label(self, labels, downcast=False):
                     new_data, index=self.index, name=labels
                 )
                 return out
-        out = self._constructor()._from_data(
+        out = self.__class__()._from_data(
             new_data, index=self.index, columns=new_data.to_pandas_index()
         )
         return out
@@ -3158,20 +3159,6 @@ def take(self, positions, keep_index=True):
         out.columns = self.columns
         return out
 
-    def __copy__(self):
-        return self.copy(deep=True)
-
-    def __deepcopy__(self, memo=None):
-        """
-        Parameters
-        ----------
-        memo, default None
-            Standard signature. Unused
-        """
-        if memo is None:
-            memo = {}
-        return self.copy(deep=True)
-
     @annotate("INSERT", color="green", domain="cudf_python")
     def insert(self, loc, name, value):
         """ Add a column to DataFrame at the index specified by loc.
@@ -7769,8 +7756,6 @@ def explode(self, column, ignore_index=False):
 
         return super()._explode(column, ignore_index)
 
-    _accessors = set()  # type: Set[Any]
-
 
 def from_pandas(obj, nan_as_null=None):
     """

python/cudf/cudf/core/frame.py

@@ -48,6 +48,12 @@ class Frame(libcudf.table.Table):
 
     _data: "ColumnAccessor"
 
+    @classmethod
+    def __init_subclass__(cls):
+        # All subclasses contain a set _accessors that is used to hold custom
+        # accessors defined by user APIs (see cudf/api/extensions/accessor.py).
+        cls._accessors = set()
+
     @classmethod
     def _from_table(cls, table: Frame):
         return cls(table._data, index=table._index)
@@ -608,7 +614,7 @@ def _get_columns_by_index(self, indices):
 
         """
         data = self._data.select_by_index(indices)
-        return self._constructor(
+        return self.__class__(
             data, columns=data.to_pandas_index(), index=self.index
         )
 
@@ -3295,6 +3301,211 @@ def _reindex(
         return self._mimic_inplace(result, inplace=inplace)
 
 
+class SingleColumnFrame(Frame):
+    """A one-dimensional frame.
+
+    Frames with only a single column share certain logic that is encoded in
+    this class.
+    """
+
+    @property
+    def name(self):
+        """The name of this object."""
+        return next(iter(self._data.names))
+
+    @name.setter
+    def name(self, value):
+        self._data[value] = self._data.pop(self.name)
+
+    @property
+    def ndim(self):
+        """Dimension of the data (always 1)."""
+        return 1
+
+    @property
+    def shape(self):
+        """Returns a tuple representing the dimensionality of the Index.
+        """
+        return (len(self),)
+
+    def __iter__(self):
+        cudf.utils.utils.raise_iteration_error(obj=self)
+
+    def __len__(self):
+        return len(self._column)
+
+    def __bool__(self):
+        raise TypeError(
+            f"The truth value of a {type(self)} is ambiguous. Use "
+            "a.empty, a.bool(), a.item(), a.any() or a.all()."
+        )
+
+    @property
+    def _column(self):
+        return self._data[self.name]
+
+    @_column.setter
+    def _column(self, value):
+        self._data[self.name] = value
+
+    @property
+    def values(self):
+        """
+        Return a CuPy representation of the data.
+
+        Returns
+        -------
+        out : cupy.ndarray
+            A device representation of the underlying data.
+
+        Examples
+        --------
+        >>> import cudf
+        >>> ser = cudf.Series([1, -10, 100, 20])
+        >>> ser.values
+        array([  1, -10, 100,  20])
+        >>> type(ser.values)
+        <class 'cupy.core.core.ndarray'>
+        >>> index = cudf.Index([1, -10, 100, 20])
+        >>> index.values
+        array([  1, -10, 100,  20])
+        >>> type(index.values)
+        <class 'cupy.core.core.ndarray'>
+        """
+        return self._column.values
+
+    @property
+    def values_host(self):
+        """
+        Return a NumPy representation of the data.
+
+        Returns
+        -------
+        out : numpy.ndarray
+            A host representation of the underlying data.
+
+        Examples
+        --------
+        >>> import cudf
+        >>> ser = cudf.Series([1, -10, 100, 20])
+        >>> ser.values_host
+        array([  1, -10, 100,  20])
+        >>> type(ser.values_host)
+        <class 'numpy.ndarray'>
+        >>> index = cudf.Index([1, -10, 100, 20])
+        >>> index.values_host
+        array([  1, -10, 100,  20])
+        >>> type(index.values_host)
+        <class 'numpy.ndarray'>
+        """
+        return self._column.values_host
+
+    def tolist(self):
+
+        raise TypeError(
+            "cuDF does not support conversion to host memory "
+            "via the `tolist()` method. Consider using "
+            "`.to_arrow().to_pylist()` to construct a Python list."
+        )
+
+    to_list = tolist
+
+    def to_gpu_array(self, fillna=None):
+        """Get a dense numba device array for the data.
+
+        Parameters
+        ----------
+        fillna : str or None
+            See *fillna* in ``.to_array``.
+
+        Notes
+        -----
+
+        if ``fillna`` is ``None``, null values are skipped.  Therefore, the
+        output size could be smaller.
+
+        Returns
+        -------
+        numba.DeviceNDArray
+
+        Examples
+        --------
+        >>> import cudf
+        >>> s = cudf.Series([10, 20, 30, 40, 50])
+        >>> s
+        0    10
+        1    20
+        2    30
+        3    40
+        4    50
+        dtype: int64
+        >>> s.to_gpu_array()
+        <numba.cuda.cudadrv.devicearray.DeviceNDArray object at 0x7f1840858890>
+        """
+        return self._column.to_gpu_array(fillna=fillna)
+
+    @classmethod
+    def from_arrow(cls, array):
+        """Create from PyArrow Array/ChunkedArray.
+
+        Parameters
+        ----------
+        array : PyArrow Array/ChunkedArray
+            PyArrow Object which has to be converted.
+
+        Raises
+        ------
+        TypeError for invalid input type.
+
+        Returns
+        -------
+        SingleColumnFrame
+
+        Examples
+        --------
+        >>> import cudf
+        >>> import pyarrow as pa
+        >>> cudf.Index.from_arrow(pa.array(["a", "b", None]))
+        StringIndex(['a' 'b' None], dtype='object')
+        >>> cudf.Series.from_arrow(pa.array(["a", "b", None]))
+        0       a
+        1       b
+        2    <NA>
+        dtype: object
+        """
+        return cls(cudf.core.column.column.ColumnBase.from_arrow(array))
+
+    def to_arrow(self):
+        """
+        Convert to a PyArrow Array.
+
+        Returns
+        -------
+        PyArrow Array
+
+        Examples
+        --------
+        >>> import cudf
+        >>> sr = cudf.Series(["a", "b", None])
+        >>> sr.to_arrow()
+        <pyarrow.lib.StringArray object at 0x7f796b0e7600>
+        [
+          "a",
+          "b",
+          null
+        ]
+        >>> ind = cudf.Index(["a", "b", None])
+        >>> ind.to_arrow()
+        <pyarrow.lib.StringArray object at 0x7f796b0e7750>
+        [
+          "a",
+          "b",
+          null
+        ]
+        """
+        return self._column.to_arrow()
+
+
 def _get_replacement_values_for_columns(
     to_replace: Any, value: Any, columns_dtype_map: Dict[Any, Any]
 ) -> Tuple[Dict[Any, bool], Dict[Any, Any], Dict[Any, Any]]: