_mixins.py

from typing import Any, Optional, Sequence, TypeVar

import numpy as np

from pandas._libs import lib
from pandas._typing import Shape
from pandas.compat.numpy import function as nv
from pandas.errors import AbstractMethodError
from pandas.util._decorators import cache_readonly, doc
from pandas.util._validators import validate_fillna_kwargs

from pandas.core.dtypes.common import is_dtype_equal
from pandas.core.dtypes.inference import is_array_like
from pandas.core.dtypes.missing import array_equivalent

from pandas.core import missing
from pandas.core.algorithms import take, unique
from pandas.core.array_algos.transforms import shift
from pandas.core.arrays.base import ExtensionArray
from pandas.core.construction import extract_array
from pandas.core.indexers import check_array_indexer

NDArrayBackedExtensionArrayT = TypeVar(
    "NDArrayBackedExtensionArrayT", bound="NDArrayBackedExtensionArray"
)


class NDArrayBackedExtensionArray(ExtensionArray):
    """
    ExtensionArray that is backed by a single NumPy ndarray.
    """

    _ndarray: np.ndarray

    def _from_backing_data(
        self: NDArrayBackedExtensionArrayT, arr: np.ndarray
    ) -> NDArrayBackedExtensionArrayT:
        """
        Construct a new ExtensionArray `new_array` with `arr` as its _ndarray.

        This should round-trip:
            self == self._from_backing_data(self._ndarray)
        """
        raise AbstractMethodError(self)

    def _box_func(self, x):
        """
        Wrap numpy type in our dtype.type if necessary.
        """
        return x

    def _validate_scalar(self, value):
        # used by NDArrayBackedExtensionIndex.insert
        raise AbstractMethodError(self)

    # ------------------------------------------------------------------------

    def take(
        self: NDArrayBackedExtensionArrayT,
        indices: Sequence[int],
        *,
        allow_fill: bool = False,
        fill_value: Any = None,
        axis: int = 0,
    ) -> NDArrayBackedExtensionArrayT:
        if allow_fill:
            fill_value = self._validate_fill_value(fill_value)

        new_data = take(
            self._ndarray,
            indices,
            allow_fill=allow_fill,
            fill_value=fill_value,
            axis=axis,
        )
        return self._from_backing_data(new_data)

    def _validate_fill_value(self, fill_value):
        """
        If a fill_value is passed to `take` convert it to a representation
        suitable for self._ndarray, raising TypeError if this is not possible.

        Parameters
        ----------
        fill_value : object

        Returns
        -------
        fill_value : native representation

        Raises
        ------
        TypeError
        """
        raise AbstractMethodError(self)

    # ------------------------------------------------------------------------

    # TODO: make this a cache_readonly; for that to work we need to remove
    #  the _index_data kludge in libreduction
    @property
    def shape(self) -> Shape:
        return self._ndarray.shape

    def __len__(self) -> int:
        return self.shape[0]

    @cache_readonly
    def ndim(self) -> int:
        return len(self.shape)

    @cache_readonly
    def size(self) -> int:
        return np.prod(self.shape)

    @cache_readonly
    def nbytes(self) -> int:
        return self._ndarray.nbytes

    def reshape(
        self: NDArrayBackedExtensionArrayT, *args, **kwargs
    ) -> NDArrayBackedExtensionArrayT:
        new_data = self._ndarray.reshape(*args, **kwargs)
        return self._from_backing_data(new_data)

    def ravel(
        self: NDArrayBackedExtensionArrayT, *args, **kwargs
    ) -> NDArrayBackedExtensionArrayT:
        new_data = self._ndarray.ravel(*args, **kwargs)
        return self._from_backing_data(new_data)

    @property
    def T(self: NDArrayBackedExtensionArrayT) -> NDArrayBackedExtensionArrayT:
        new_data = self._ndarray.T
        return self._from_backing_data(new_data)

    # ------------------------------------------------------------------------

    def equals(self, other) -> bool:
        if type(self) is not type(other):
            return False
        if not is_dtype_equal(self.dtype, other.dtype):
            return False
        return bool(array_equivalent(self._ndarray, other._ndarray))

    def _values_for_argsort(self):
        return self._ndarray

    def copy(self: NDArrayBackedExtensionArrayT) -> NDArrayBackedExtensionArrayT:
        new_data = self._ndarray.copy()
        return self._from_backing_data(new_data)

    def repeat(
        self: NDArrayBackedExtensionArrayT, repeats, axis=None
    ) -> NDArrayBackedExtensionArrayT:
        """
        Repeat elements of an array.

        See Also
        --------
        numpy.ndarray.repeat
        """
        nv.validate_repeat(tuple(), dict(axis=axis))
        new_data = self._ndarray.repeat(repeats, axis=axis)
        return self._from_backing_data(new_data)

    def unique(self: NDArrayBackedExtensionArrayT) -> NDArrayBackedExtensionArrayT:
        new_data = unique(self._ndarray)
        return self._from_backing_data(new_data)

    @classmethod
    @doc(ExtensionArray._concat_same_type)
    def _concat_same_type(cls, to_concat, axis: int = 0):
        dtypes = {str(x.dtype) for x in to_concat}
        if len(dtypes) != 1:
            raise ValueError("to_concat must have the same dtype (tz)", dtypes)

        new_values = [x._ndarray for x in to_concat]
        new_values = np.concatenate(new_values, axis=axis)
        return to_concat[0]._from_backing_data(new_values)

    @doc(ExtensionArray.searchsorted)
    def searchsorted(self, value, side="left", sorter=None):
        value = self._validate_searchsorted_value(value)
        return self._ndarray.searchsorted(value, side=side, sorter=sorter)

    def _validate_searchsorted_value(self, value):
        return value

    @doc(ExtensionArray.shift)
    def shift(self, periods=1, fill_value=None, axis=0):

        fill_value = self._validate_shift_value(fill_value)
        new_values = shift(self._ndarray, periods, axis, fill_value)

        return self._from_backing_data(new_values)

    def _validate_shift_value(self, fill_value):
        # TODO: after deprecation in datetimelikearraymixin is enforced,
        #  we can remove this and ust validate_fill_value directly
        return self._validate_fill_value(fill_value)

    def __setitem__(self, key, value):
        key = check_array_indexer(self, key)
        value = self._validate_setitem_value(value)
        self._ndarray[key] = value

    def _validate_setitem_value(self, value):
        return value

    def __getitem__(self, key):
        if lib.is_integer(key):
            # fast-path
            result = self._ndarray[key]
            if self.ndim == 1:
                return self._box_func(result)
            return self._from_backing_data(result)

        key = extract_array(key, extract_numpy=True)
        key = check_array_indexer(self, key)
        result = self._ndarray[key]
        if lib.is_scalar(result):
            return self._box_func(result)

        result = self._from_backing_data(result)
        return result

    @doc(ExtensionArray.fillna)
    def fillna(
        self: NDArrayBackedExtensionArrayT, value=None, method=None, limit=None
    ) -> NDArrayBackedExtensionArrayT:
        value, method = validate_fillna_kwargs(value, method)

        mask = self.isna()

        # TODO: share this with EA base class implementation
        if is_array_like(value):
            if len(value) != len(self):
                raise ValueError(
                    f"Length of 'value' does not match. Got ({len(value)}) "
                    f" expected {len(self)}"
                )
            value = value[mask]

        if mask.any():
            if method is not None:
                func = missing.get_fill_func(method)
                new_values = func(self._ndarray.copy(), limit=limit, mask=mask)
                # TODO: PandasArray didnt used to copy, need tests for this
                new_values = self._from_backing_data(new_values)
            else:
                # fill with value
                new_values = self.copy()
                new_values[mask] = value
        else:
            new_values = self.copy()
        return new_values

    # ------------------------------------------------------------------------
    # Reductions

    def _reduce(self, name: str, *, skipna: bool = True, **kwargs):
        meth = getattr(self, name, None)
        if meth:
            return meth(skipna=skipna, **kwargs)
        else:
            msg = f"'{type(self).__name__}' does not implement reduction '{name}'"
            raise TypeError(msg)

    def _wrap_reduction_result(self, axis: Optional[int], result):
        if axis is None or self.ndim == 1:
            return self._box_func(result)
        return self._from_backing_data(result)

    # ------------------------------------------------------------------------

    def __repr__(self) -> str:
        if self.ndim == 1:
            return super().__repr__()

        from pandas.io.formats.printing import format_object_summary

        # the short repr has no trailing newline, while the truncated
        # repr does. So we include a newline in our template, and strip
        # any trailing newlines from format_object_summary
        lines = [
            format_object_summary(x, self._formatter(), indent_for_name=False).rstrip(
                ", \n"
            )
            for x in self
        ]
        data = ",\n".join(lines)
        class_name = f"<{type(self).__name__}>"
        return f"{class_name}\n[\n{data}\n]\nShape: {self.shape}, dtype: {self.dtype}"