ak.contents.BitMaskedArray
--------------------------

.. py:module: ak.contents.BitMaskedArray

Defined in `awkward.contents.bitmaskedarray <https://github.com/scikit-hep/awkward/blob/e9dd2694cf5c6ccb1717358fe926816d8ecbfb9c/src/awkward/contents/bitmaskedarray.py>`__ on `line 52 <https://github.com/scikit-hep/awkward/blob/e9dd2694cf5c6ccb1717358fe926816d8ecbfb9c/src/awkward/contents/bitmaskedarray.py#L52>`__.

.. py:class:: ak.contents.BitMaskedArray(self, mask, content, valid_when, length, lsb_order, *, parameters=None)

Like :py:obj:`ak.contents.ByteMaskedArray`, BitMaskedArray implements an
:py:obj:`ak.types.OptionType` with two buffers, ``mask`` and ``content``.
However, the boolean ``mask`` values are packed into a bitmap.

BitMaskedArray has an additional parameter, ``lsb_order``; if True,
the position of each bit is in
`Least-Significant Bit order <https://en.wikipedia.org/wiki/Bit_numbering>`__
(LSB):

.. code-block:: python


    is_valid[j] = bool(mask[j // 8] & (1 << (j % 8))) == valid_when

If False, the position of each bit is in Most-Significant Bit order
(MSB):

.. code-block:: python


    is_valid[j] = bool(mask[j // 8] & (128 >> (j % 8))) == valid_when

If the logical size of the buffer is not a multiple of 8, the ``mask``
has to be padded. Thus, an explicit ``length`` is also part of the
class's definition.

This is equivalent to *all* of Apache Arrow's array types because they all
`use bitmaps <https://arrow.apache.org/docs/format/Columnar.html#validity-bitmaps>`__
to mask their data, with ``valid_when=True`` and ``lsb_order=True``.

To illustrate how the constructor arguments are interpreted, the following is a
simplified implementation of ``__init__``, ``__len__``, and ``__getitem__``:

.. code-block:: python


    class BitMaskedArray(Content):
        def __init__(self, mask, content, valid_when, length, lsb_order):
            assert isinstance(mask, IndexU8)
            assert isinstance(content, Content)
            assert isinstance(valid_when, bool)
            assert isinstance(length, int) and length >= 0
            assert isinstance(lsb_order, bool)
            assert len(mask) <= len(content)
            self.mask = mask
            self.content = content
            self.valid_when = valid_when
            self.length = length
            self.lsb_order = lsb_order

        def __len__(self):
            return self.length

        def __getitem__(self, where):
            if isinstance(where, int):
                if where < 0:
                    where += len(self)
                assert 0 <= where < len(self)
                if self.lsb_order:
                    bit = bool(self.mask[where // 8] & (1 << (where % 8)))
                else:
                    bit = bool(self.mask[where // 8] & (128 >> (where % 8)))
                if bit == self.valid_when:
                    return self.content[where]
                else:
                    return None

            elif isinstance(where, slice) and where.step is None:
                # In general, slices must convert BitMaskedArray to ByteMaskedArray.
                bytemask = np.unpackbits(
                    self.mask, bitorder=("little" if self.lsb_order else "big")
                ).view(bool)
                return ByteMaskedArray(
                    bytemask[where.start : where.stop],
                    self.content[where.start : where.stop],
                    valid_when=self.valid_when,
                )

            elif isinstance(where, str):
                return BitMaskedArray(
                    self.mask,
                    self.content[where],
                    valid_when=self.valid_when,
                    length=self.length,
                    lsb_order=self.lsb_order,
                )

            else:
                raise AssertionError(where)



.. _ak-contents-bitmaskedarray-mask:

.. py:attribute:: ak.contents.BitMaskedArray.mask



.. _ak-contents-bitmaskedarray-valid_when:

.. py:attribute:: ak.contents.BitMaskedArray.valid_when



.. _ak-contents-bitmaskedarray-lsb_order:

.. py:attribute:: ak.contents.BitMaskedArray.lsb_order



.. _ak-contents-bitmaskedarray-copy:

.. py:method:: ak.contents.BitMaskedArray.copy(self, mask=UNSET, content=UNSET, valid_when=UNSET, length=UNSET, lsb_order=UNSET, *, parameters=UNSET)



.. _ak-contents-bitmaskedarray-__copy__:

.. py:method:: ak.contents.BitMaskedArray.__copy__(self)



.. _ak-contents-bitmaskedarray-__deepcopy__:

.. py:method:: ak.contents.BitMaskedArray.__deepcopy__(self, memo)



.. _ak-contents-bitmaskedarray-simplified:

.. py:method:: ak.contents.BitMaskedArray.simplified(cls, mask, content, valid_when, length, lsb_order, *, parameters=None)



.. _ak-contents-bitmaskedarray-_form_with_key:

.. py:method:: ak.contents.BitMaskedArray._form_with_key(self, getkey)



.. _ak-contents-bitmaskedarray-_to_buffers:

.. py:method:: ak.contents.BitMaskedArray._to_buffers(self, form, getkey, container, backend, byteorder)



.. _ak-contents-bitmaskedarray-_to_typetracer:

.. py:method:: ak.contents.BitMaskedArray._to_typetracer(self, forget_length)



.. _ak-contents-bitmaskedarray-_touch_data:

.. py:method:: ak.contents.BitMaskedArray._touch_data(self, recursive)



.. _ak-contents-bitmaskedarray-_touch_shape:

.. py:method:: ak.contents.BitMaskedArray._touch_shape(self, recursive)



.. _ak-contents-bitmaskedarray-length:

.. py:attribute:: ak.contents.BitMaskedArray.length



.. _ak-contents-bitmaskedarray-__repr__:

.. py:method:: ak.contents.BitMaskedArray.__repr__(self)



.. _ak-contents-bitmaskedarray-_repr:

.. py:method:: ak.contents.BitMaskedArray._repr(self, indent, pre, post)



.. _ak-contents-bitmaskedarray-to_indexedoptionarray64:

.. py:method:: ak.contents.BitMaskedArray.to_IndexedOptionArray64(self)



.. _ak-contents-bitmaskedarray-to_bytemaskedarray:

.. py:method:: ak.contents.BitMaskedArray.to_ByteMaskedArray(self)



.. _ak-contents-bitmaskedarray-to_bitmaskedarray:

.. py:method:: ak.contents.BitMaskedArray.to_BitMaskedArray(self, valid_when, lsb_order)



.. _ak-contents-bitmaskedarray-mask_as_bool:

.. py:method:: ak.contents.BitMaskedArray.mask_as_bool(self, valid_when=None)



.. _ak-contents-bitmaskedarray-_getitem_nothing:

.. py:method:: ak.contents.BitMaskedArray._getitem_nothing(self)



.. _ak-contents-bitmaskedarray-_is_getitem_at_placeholder:

.. py:method:: ak.contents.BitMaskedArray._is_getitem_at_placeholder(self)



.. _ak-contents-bitmaskedarray-_getitem_at:

.. py:method:: ak.contents.BitMaskedArray._getitem_at(self, where)



.. _ak-contents-bitmaskedarray-_getitem_range:

.. py:method:: ak.contents.BitMaskedArray._getitem_range(self, start, stop)



.. _ak-contents-bitmaskedarray-_getitem_field:

.. py:method:: ak.contents.BitMaskedArray._getitem_field(self, where, only_fields=())



.. _ak-contents-bitmaskedarray-_getitem_fields:

.. py:method:: ak.contents.BitMaskedArray._getitem_fields(self, where, only_fields=())



.. _ak-contents-bitmaskedarray-_carry:

.. py:method:: ak.contents.BitMaskedArray._carry(self, carry, allow_lazy)



.. _ak-contents-bitmaskedarray-_getitem_next_jagged:

.. py:method:: ak.contents.BitMaskedArray._getitem_next_jagged(self, slicestarts, slicestops, slicecontent, tail)



.. _ak-contents-bitmaskedarray-_getitem_next:

.. py:method:: ak.contents.BitMaskedArray._getitem_next(self, head, tail, advanced)



.. _ak-contents-bitmaskedarray-project:

.. py:method:: ak.contents.BitMaskedArray.project(self, mask=None)



.. _ak-contents-bitmaskedarray-_offsets_and_flattened:

.. py:method:: ak.contents.BitMaskedArray._offsets_and_flattened(self, axis, depth)



.. _ak-contents-bitmaskedarray-_mergeable_next:

.. py:method:: ak.contents.BitMaskedArray._mergeable_next(self, other, mergebool)



.. _ak-contents-bitmaskedarray-_reverse_merge:

.. py:method:: ak.contents.BitMaskedArray._reverse_merge(self, other)



.. _ak-contents-bitmaskedarray-_mergemany:

.. py:method:: ak.contents.BitMaskedArray._mergemany(self, others)



.. _ak-contents-bitmaskedarray-_fill_none:

.. py:method:: ak.contents.BitMaskedArray._fill_none(self, value)



.. _ak-contents-bitmaskedarray-_local_index:

.. py:method:: ak.contents.BitMaskedArray._local_index(self, axis, depth)



.. _ak-contents-bitmaskedarray-_numbers_to_type:

.. py:method:: ak.contents.BitMaskedArray._numbers_to_type(self, name, including_unknown)



.. _ak-contents-bitmaskedarray-_is_unique:

.. py:method:: ak.contents.BitMaskedArray._is_unique(self, negaxis, starts, parents, outlength)



.. _ak-contents-bitmaskedarray-_unique:

.. py:method:: ak.contents.BitMaskedArray._unique(self, negaxis, starts, parents, outlength)



.. _ak-contents-bitmaskedarray-_argsort_next:

.. py:method:: ak.contents.BitMaskedArray._argsort_next(self, negaxis, starts, shifts, parents, outlength, ascending, stable)



.. _ak-contents-bitmaskedarray-_sort_next:

.. py:method:: ak.contents.BitMaskedArray._sort_next(self, negaxis, starts, parents, outlength, ascending, stable)



.. _ak-contents-bitmaskedarray-_combinations:

.. py:method:: ak.contents.BitMaskedArray._combinations(self, n, replacement, recordlookup, parameters, axis, depth)



.. _ak-contents-bitmaskedarray-_reduce_next:

.. py:method:: ak.contents.BitMaskedArray._reduce_next(self, reducer, negaxis, starts, shifts, parents, outlength, mask, keepdims, behavior)



.. _ak-contents-bitmaskedarray-_validity_error:

.. py:method:: ak.contents.BitMaskedArray._validity_error(self, path)



.. _ak-contents-bitmaskedarray-_nbytes_part:

.. py:method:: ak.contents.BitMaskedArray._nbytes_part(self)



.. _ak-contents-bitmaskedarray-_pad_none:

.. py:method:: ak.contents.BitMaskedArray._pad_none(self, target, axis, depth, clip)



.. _ak-contents-bitmaskedarray-_to_arrow:

.. py:method:: ak.contents.BitMaskedArray._to_arrow(self, pyarrow, mask_node, validbytes, length, options)



.. _ak-contents-bitmaskedarray-_to_backend_array:

.. py:method:: ak.contents.BitMaskedArray._to_backend_array(self, allow_missing, backend)



.. _ak-contents-bitmaskedarray-_remove_structure:

.. py:method:: ak.contents.BitMaskedArray._remove_structure(self, backend, options)



.. _ak-contents-bitmaskedarray-_drop_none:

.. py:method:: ak.contents.BitMaskedArray._drop_none(self)



.. _ak-contents-bitmaskedarray-_recursively_apply:

.. py:method:: ak.contents.BitMaskedArray._recursively_apply(self, action, depth, depth_context, lateral_context, options)



.. _ak-contents-bitmaskedarray-to_packed:

.. py:method:: ak.contents.BitMaskedArray.to_packed(self, recursive=True)



.. _ak-contents-bitmaskedarray-_to_list:

.. py:method:: ak.contents.BitMaskedArray._to_list(self, behavior, json_conversions)



.. _ak-contents-bitmaskedarray-_to_backend:

.. py:method:: ak.contents.BitMaskedArray._to_backend(self, backend)



.. _ak-contents-bitmaskedarray-_is_equal_to:

.. py:method:: ak.contents.BitMaskedArray._is_equal_to(self, other, index_dtype, numpyarray, all_parameters)