.. currentmodule:: bitstring

.. note::
    The Array class is new in version 4.1 of bitstring, and is considered a 'beta' feature for now.
    There may be some small changes in future point releases and it hasn't been tested as well as the rest of the library.

    This documentation may also be a bit 'beta'.


Array Class
===========

.. class:: Array(fmt: str[, initializer[, trailing_bits]])

    Create a new ``Array`` whose elements are set by the ``fmt`` string.
    This can be any format which has a fixed length.
    See :ref:`format_tokens` and :ref:`compact_format` for details on allowed format strings, noting that only formats with well defined bit lengths are allowed.

    The ``Array`` class is a way to efficiently store data that has a single type with a set length.
    The ``bitstring.Array`` type is meant as a more flexible version of the standard ``array.array``, and can be used the same way. ::

        import array
        import bitstring

        x = array.array('f', [1.0, 2.0, 3.14])
        y = bitstring.Array('=f', [1.0, 2.0, 3.14])

        assert x.tobytes() == y.tobytes()

    This example packs three 32-bit floats into objects using both libraries.
    The only difference is the explicit native endianness for the format string of the bitstring version.
    The bitstring Array's advantage lies in the way that any fixed-length bitstring format can be used instead of just the dozen or so typecodes supported by the ``array`` module.

    For example ``'uint4'``, ``'bfloat'`` or ``'hex12'`` can be used, and the endianness of multi-byte formats can be properly specified.

    Each element in the ``Array`` must then be something that makes sense for the ``fmt``.
    Some examples will help illustrate::

        from bitstring import Array

        # Each unsigned int is stored in 4 bits
        a = Array('uint4', [0, 5, 5, 3, 2])

        # Convert and store floats in 8 bits each
        b = Array('float8_152', [-56.0, 0.123, 99.6])

        # Each element is a  7 bit signed integer
        c = Array('int7', [-3, 0, 120])

    You can then access and modify the ``Array`` with the usual notation::

        a[1:4]  # Array('uint4', [5, 5, 3])
        b[0]    # -56.0
        c[-1]   # 120

        a[0] = 2
        b.extend([0.0, -1.5])

    Conversion between ``Array`` types can be done by creating a new one with the new format from the elements of the other one.
    If elements of the old array don't fit or don't make sense in the new array then the relevant exceptions will be raised. ::

        >>> x = Array('float64', [89.3, 1e34, -0.00000001, 34])
        >>> y = Array('float16', x.tolist())
        >>> y
        Array('float16', [89.3125, inf, -0.0, 34.0])
        >>> y = Array('float8_143', y.tolist())
        >>> y
        Array('float8_143', [88.0, 240.0, 0.0, 32.0])
        >>> Array('uint8', y.tolist())
        Array('uint8', [88, 240, 0, 32])
        >>> Array('uint7', y.tolist())
        bitstring.CreationError: 240 is too large an unsigned integer for a bitstring of length 7. The allowed range is [0, 127].

    You can also reinterpret the data by changing the ``fmt`` property directly.
    This will not copy any data but will cause the current data to be shown differently. ::

        >>> x = Array('int16', [-5, 100, -4])
        >>> x
        Array('int16', [-5, 100, -4])
        >>> x.fmt = 'int8'
        >>> x
        Array('int8', [-1, -5, 0, 100, -1, -4])


    The data for the array is stored internally as a ``BitArray`` object.
    It can be directly accessed using the ``data`` property.
    You can freely manipulate the internal data using all of the methods available for the ``BitArray`` class.

    The ``Array`` object also has a ``trailing_bits`` read-only data member, which consists of the end bits of the ``data`` ``BitArray`` that are left over when the ``Array`` is interpreted using ``fmt``.
    Typically ``trailing_bits`` will be an empty ``BitArray`` but if you change the length of the ``data`` or change the ``fmt`` specification there may be some bits left over.

    Some methods, such as ``append`` and ``extend`` will raise an exception if used when ``trailing_bits`` is not empty, as it not clear how these should behave in this case. You can however still use ``insert`` which will always leave the ``trailing_bits`` unchanged.



    The ``fmt`` string can be a type code such as ``'>H'`` or ``'=d'`` but it can also be a string defining any format which has a fixed-length in bits, for example ``'int12'``, ``'bfloat'``, ``'bytes5'`` or ``'bool'``.

    Note that the typecodes must include an endianness character to give the byte ordering.
    This is more like the ``struct`` module typecodes, and is different to the ``array.array`` typecodes which are always native-endian.

    The correspondence between the big-endian type codes and bitstring format codes is given in the table below.

    =========   ===================
    Type code   bitstring format
    =========   ===================
    ``'>b'``     ``'int8'``
    ``'>B'``     ``'uint8'``
    ``'>h'``     ``'int16'``
    ``'>H'``     ``'uint16'``
    ``'>l'``     ``'int32'``
    ``'>L'``     ``'uint32'``
    ``'>q'``     ``'int64'``
    ``'>Q'``     ``'uint64'``
    ``'>e'``     ``'float16'``
    ``'>f'``     ``'float32'``
    ``'>d'``     ``'float64'``
    =========   ===================

    The endianness character can be ``'>'`` for big-endian, ``'<'`` for little-endian or ``'='`` for native-endian (``'@'`` can also be used for native-endian).
    In the bitstring formats the default is big-endian, but you can specify little or native endian using ``'le'`` or ``'ne'`` modifiers, for example:

    ============  =============================
    Type code     bitstring format
    ============  =============================
    ``'>H'``      ``'uint16'`` / ``'uintbe16'``
    ``'=H'``      ``'uintne16'``
    ``'<H'``      ``'uintle16'``
    ============  =============================


    Note that:

    * The ``array`` module's native endianness means that different packed binary data will be created on different types of machines.
      Users may find that behaviour unexpected which is why endianness must be explicitly given as in the rest of the bitstring module.

    * The ``'u'`` type code from the ``array`` module isn't supported as its length is platform dependent.

    * The ``'e'`` type code isn't one of the ``array`` supported types, but it is used in the ``struct`` module and we support it here.

    * The ``'b'`` and ``'B'`` type codes need to be preceded by an endianness character even though it makes no difference which one you use as they are only 1 byte long.


Methods
-------

    .. note::
        Some methods that are available for ``array.array`` objects are deliberately omitted in this interface as they don't really add much.
        In particular, some omissions and their suggested replacements are:

        ``a.fromlist(alist)`` → ``a.extend(alist)``

        ``a.frombytes(s)`` → ``a.data.extend(s)``


    .. method:: Array.append(x: float | int | str | bytes) -> None

        Add a new element with value `x` to the end of the Array.
        The type of `x` should be appropriate for the type of the Array.

        Raises a ``ValueError`` if the Array's bit length is not a multiple of its format length (see :attr:`~Array.trailing_bits`).

    .. method:: Array.byteswap() -> None

        Change the byte endianness of each element.

        Raises a ``ValueError`` if the format is not an integer number of bytes long. ::

            >>> a = Array('uint32', [100, 1, 999])
            >>> a.byteswap()
            >>> a
            Array('uint32', [1677721600, 16777216, 3875733504])
            >>> a.fmt = 'uintle32'
            >>> a
            Array('uintle32', [100, 1, 999])

    .. method:: Array.count(value: float | int | str | bytes) -> int

        Returns the number of elements set to *value*. ::

            >>> a = Array('hex4')
            >>> a.data += '0xdeadbeef'
            >>> a
            Array('hex4', ['d', 'e', 'a', 'd', 'b', 'e', 'e', 'f'])
            >>> a.count('e')
            3

        For floating point types using a `value` of ``float('nan')`` will count the number of elements for which ``math.isnan()`` returns ``True``.

    .. method:: Array.extend(iterable: Iterable | Array) -> None

        Extend the Array by constructing new elements from the values in a list or other iterable.

        The `iterable` can be another ``Array`` or an ``array.array``, but only if the format is the same. ::

            >>> a = Array('int5', [-5, 0, 10])
            >>> a.extend([3, 2, 1])
            >>> a.extend(a[0:3] // 5)
            >>> a
            Array('int5', [-5, 0, 10, 3, 2, 1, -1, 0, 2])

    .. method:: Array.fromfile(f: BinaryIO, n: int | None) -> None

        Append items read from a file object.

    .. method:: Array.insert(i: int, x: float | int | str | bytes) -> None

        Insert an item at a given position. ::

            >>> a = Array('float8_152', [-10, -5, -0.5, 5, 10])
            >>> a.insert(3, 0.5)
            >>> a
            Array('float8_152', [-10.0, -5.0, -0.5, 0.5, 5.0, 10.0])


    .. method:: Array.pop(i: int | None) -> float | int | str | bytes

        Remove and return the item at position i.

        If a position isn't specified the final item is returned and removed. ::

            >>> Array('bytes3', [b'ABC', b'DEF', b'ZZZ'])
            >>> a.pop(0)
            b'ABC'
            >>> a.pop()
            b'ZZZ'
            >>> a.pop()
            b'DEF'


    .. method:: Array.pp(fmt: str | None, width: int, show_offset: bool, stream: TextIO) -> None

        Pretty print the Array.

        `fmt` defaults to the Array's current format, but any other valid Array format string, or pair of comma-separated format strings can be used.

        The output will try to stay within `width` characters per line, but will always output at least one element value.

        Setting `show_offset` to ``True`` will add a element index to each line of the output.

        An output `stream` can be specified. This should be an object with a ``write`` method and the default is ``sys.stdout``.

            >>> a = Array('u20', bytearray(range(100)))
            >>> a.pp(width=70)
            <Array fmt='u20', length=40, itemsize=20 bits, total data size=100 bytes>
            [
                 16  131844   20576  460809   41136  789774   61697   70163
              82257  399128  102817  728093  123378    8482  143938  337447
             164498  666412  185058  995377  205619  275766  226179  604731
             246739  933696  267300  214085  287860  543050  308420  872015
             328981  152404  349541  481369  370101  810334  390662   90723
            ]

            >>> a.pp('hex32', width=70)
            <Array fmt='hex32', length=25, itemsize=32 bits, total data size=100 bytes>
            [
            00010203 04050607 08090a0b 0c0d0e0f 10111213 14151617 18191a1b
            1c1d1e1f 20212223 24252627 28292a2b 2c2d2e2f 30313233 34353637
            38393a3b 3c3d3e3f 40414243 44454647 48494a4b 4c4d4e4f 50515253
            54555657 58595a5b 5c5d5e5f 60616263
            ]

            >>> a.pp('i12, hex', show_offset=True, width=70)
            <Array fmt='i12, hex', length=114, itemsize=7 bits, total data size=100 bytes>
            [
                0   258    48  1029    96  1800 : 000 102 030 405 060 708
              144 -1525   192  -754   241    17 : 090 a0b 0c0 d0e 0f1 011
              289   788   337  1559   385 -1766 : 121 314 151 617 181 91a
              433  -995   481  -224   530   547 : 1b1 c1d 1e1 f20 212 223
              578  1318   626 -2007   674 -1236 : 242 526 272 829 2a2 b2c
              722  -465   771   306   819  1077 : 2d2 e2f 303 132 333 435
              867  1848   915 -1477   963  -706 : 363 738 393 a3b 3c3 d3e
             1012    65  1060   836  1108  1607 : 3f4 041 424 344 454 647
             1156 -1718  1204  -947  1252  -176 : 484 94a 4b4 c4d 4e4 f50
             1301   595  1349  1366  1397 -1959 : 515 253 545 556 575 859
             1445 -1188  1493  -417  1542   354 : 5a5 b5c 5d5 e5f 606 162
            ] + trailing_bits = 0x63

    .. method:: Array.reverse() -> None

        Reverse the order of all items in the Array. ::

            >>> a = Array('>L', [100, 200, 300])
            >>> a.reverse()
            >>> a
            Array('>L', [300, 200, 100])

    .. method:: Array.tobytes() -> bytes

        Return Array data as bytes object, padding with zero bits at the end if needed. ::

            >>> a = Array('i4', [3, -6, 2, -3, 2, -7])
            >>> a.tobytes()
            b':-)'

    .. method:: Array.tofile(f: BinaryIO) -> None

        Write Array data to a file, padding with zero bits at the end if needed.

    .. method:: Array.tolist() -> List[float | int | str | bytes]

        Return Array items as a list.

        Each packed element of the Array is converted to an ordinary Python object such as a ``float`` or an ``int`` depending on the Array's format, and returned in a Python list.

        This can be helpful if you want to use an Array to create a new Array with a different format. ::

            >>> a = Array('float16', b'some_long_byte_data?')
            >>> a
            Array('float16', [15224.0, 5524.0, 475.0, 7608.0, 1887.0, 828.5, 18000.0, 473.0, 698.0, 671.5])
            >>> b = Array('float8_152', a.tolist())
            >>> b
            Array('float8_152', [14336.0, 5120.0, 448.0, 7168.0, 1792.0, 768.0, 16384.0, 448.0, 640.0, 640.0])
            >>> b.tobytes()
            b'wqcskfxcee'


Special Methods
---------------

    .. method:: Array.__len__(self) -> int

        ``len(a)``

        Return the number of elements in the Array. ::

            >>> a = Array('uint20', [1, 2, 3])
            >>> len(a)
            3
            >>> a.fmt = 'uint1'
            >>> len(a)
            60


    .. method:: Array.__eq__(self, other) -> bool

        ``a1 == a2``

        Equality test - `other` can be either another bitstring Array or an ``array``.
        To be equal the formats must be equivalent and the underlying bit data must be the same. ::

            >>> a = Array('u8', [1, 2, 3, 2, 1])
            >>> a[0:3] == a[-1:-4:-1]
            True

        To compare only the values contained in the Array, extract them using :meth:`~Array.tolist` first.

    .. method:: Array.__ne__(self, other) -> bool

        ``a1 != a2``


    .. method:: Array.__getitem__(self, key: int | slice) -> float | int | str | bytes | Array

        ``a[i]``

        ``a[start:end:step]``

    .. method:: Array.__add__(other: int | float) -> Array

        ``a + x``


    .. method:: Array.__sub__(self, other: int | float) -> Array

        ``a - x``

    .. method:: Array.__mul__(self, other: int | float) -> Array

        ``a * x``

    .. method:: Array.__truediv__(self, other: int | float) -> Array

        ``a / x``

    .. method:: Array.__floordiv__(self, other: int | float) -> Array

        ``a // x``

    .. method:: Array.__rshift__(self, other: int) -> Array

        ``a >> i``

    .. method:: Array.__lshift__(self, other: int) -> Array

        ``a << i``

    .. method:: Array.__and__(self, other: Bits) -> Array

        ``a & bs``

    .. method:: Array.__or__(self, other: Bits) -> Array

        ``a | bs``

    .. method:: Array.__xor__(self, other: Bits) -> Array

        ``a ^ bs``

    .. method:: Array.__setitem__(self, key: int | slice, value) -> None

        ``a[i] = x``

        ``a[start:end:step] = x``

    .. method:: Array.__delitem__(self, key: int | slice) -> None

        ``del a[i]``

        ``del[start:end:step]``

    .. method:: Array.__iadd__(self, other: int | float) -> None

        In-place version of :meth:`+ <Array.__add__>`. ::

            >>> a += 3


    .. method:: Array.__isub__(self, other: int | float) -> None

        In-place version of :meth:`- <Array.__sub__>`. ::

            >>> a -= 9.4


    .. method:: Array.__imul__(self, other: int | float) -> None

        In-place version of :meth:`* <Array.__mul__>`. ::

            >>> a *= 2

    .. method:: Array.__itruediv__(self, other: int | float) -> None

        In-place version of :meth:`/ <Array.__truediv__>`. ::

            >>> a /= 5.1

    .. method:: Array.__ifloordiv__(self, other: int | float) -> None

        In-place version of :meth:`// <Array.__floordiv__>`. ::

            >>> a //= 8


    .. method:: Array.__irshift__(self, other: int) -> None

        In-place version of :meth:`>> <Array.__rshift__>`. ::

            >>> a >>= 1

    .. method:: Array.__ilshift__(self, other: int) -> None

        In-place version of :meth:`\<\< <Array.__lshift__>`. ::

            >>> a <<= 2


    .. method:: Array.__iand__(self, other: Bits) -> None

        In-place version of :meth:`& <Array.__and__>`. ::

            >>> a &= '0b1110'

    .. method:: Array.__ior__(self, other: Bits) -> None

        In-place version of :meth:`| <Array.__or__>`. ::

            >>> a |= '0x7fff'

    .. method:: Array.__ixor__(self, other: Bits) -> None

        In-place version of :meth:`^ <Array.__xor__>`. ::

            >>> a ^= bytearray([56, 23])


Properties
----------

    .. attribute:: Array.data

        The bit data of the ``Array``, as a ``BitArray``. Read and write, and can be freely manipulated with all of ``BitArray`` methods.

        Note that some ``Array`` methods such as ``append`` and ``extend`` require the  ``data`` to have a length that is a multiple of the ``Array``'s ``itemsize``.

    .. attribute:: Array.fmt

        The format string used to initialise the ``Array`` type. Read and write.

        Changing the format for an already formed ``Array`` will cause all of the bit data to be reinterpreted and can change the length of the ``Array``.
        However, changing the format won't change the underlying bit data in any way.

        Note that some ``Array`` methods such as ``append`` and ``extend`` require the bit data to have a length that is a multiple of the ``Array``'s ``itemsize``.

    .. attribute:: Array.itemsize

        The size *in bits* of each item in the ``Array``. Read-only.

        Note that this gives a value in bits, unlike the equivalent in the ``array`` module which gives a value in bytes. ::

            >>> a = Array('>h')
            >>> b = Array('bool')
            >>> a.itemsize
            16
            >>> b.itemsize
            1

    .. attribute:: Array.trailing_bits

        A ``BitArray`` object equal to the end of the ``data`` that is not a multiple of the ``itemsize``. Read only.

        This will typically be an empty ``BitArray``, but if an the ``fmt`` or the ``data`` of an ``Array`` object has been altered after its creation then there may be left-over bits at the end of the data.

        Note that any methods that append items to the ``Array`` will fail with a ``ValueError`` if there are any trailing bits.


