Method _where

pandas/core/generic.py:9970–10140

Equivalent to public method `where`, except that `other` is not applied as a function even if callable. Used in __setitem__.

(
        self,
        cond,
        other=lib.no_default,
        *,
        inplace: bool = False,
        axis: Axis | None = None,
        level=None,
    )

    @final
    def _where(
        self,
        cond,
        other=lib.no_default,
        *,
        inplace: bool = False,
        axis: Axis | None = None,
        level=None,
    ) -> Self:
        """
        Equivalent to public method `where`, except that `other` is not
        applied as a function even if callable. Used in __setitem__.
        """
        inplace = validate_bool_kwarg(inplace, "inplace")

        if axis is not None:
            axis = self._get_axis_number(axis)

        # align the cond to same shape as myself
        cond = common.apply_if_callable(cond, self)
        if isinstance(cond, NDFrame):
            # CoW: Make sure reference is not kept alive
            if cond.ndim == 1 and self.ndim == 2:
                cond = cond._constructor_expanddim(
                    dict.fromkeys(range(len(self.columns)), cond),
                    copy=False,
                )
                cond.columns = self.columns
            cond = cond.align(self, join="right")[0]
        else:
            if not hasattr(cond, "shape"):
                cond = np.asanyarray(cond)
            if cond.shape != self.shape:
                raise ValueError("Array conditional must be same shape as self")
            cond = self._constructor(cond, **self._construct_axes_dict(), copy=False)

        # make sure we are boolean
        fill_value = bool(inplace)
        cond = cond.fillna(fill_value)
        cond = cond.infer_objects()

        msg = "Boolean array expected for the condition, not {dtype}"

        if not cond.empty:
            if not isinstance(cond, ABCDataFrame):
                # This is a single-dimensional object.
                if not is_bool_dtype(cond):
                    raise TypeError(msg.format(dtype=cond.dtype))
            else:
                for block in cond._mgr.blocks:
                    if not is_bool_dtype(block.dtype):
                        raise TypeError(msg.format(dtype=block.dtype))
                if cond._mgr.any_extension_types:
                    # GH51574: avoid object ndarray conversion later on
                    cond = cond._constructor(
                        cond.to_numpy(dtype=bool, na_value=fill_value),
                        **cond._construct_axes_dict(),
                    )