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Reference
=========
bitarray version: 3.6.1 -- `change log <https://github.com/ilanschnell/bitarray/blob/master/doc/changelog.rst>`__
In the following, ``item`` and ``value`` are usually a single bit -
an integer 0 or 1.
Also, ``sub_bitarray`` refers to either a bitarray, or an ``item``.
The bitarray object:
--------------------
``bitarray(initializer=0, /, endian='big', buffer=None)`` -> bitarray
Return a new bitarray object whose items are bits initialized from
the optional initializer, and bit-endianness.
The initializer may be one of the following types:
a.) ``int`` bitarray, initialized to zeros, of given length
b.) ``bytes`` or ``bytearray`` to initialize buffer directly
c.) ``str`` of 0s and 1s, ignoring whitespace and "_"
d.) iterable of integers 0 or 1.
Optional keyword arguments:
``endian``: Specifies the bit-endianness of the created bitarray object.
Allowed values are ``big`` and ``little`` (the default is ``big``).
The bit-endianness effects the buffer representation of the bitarray.
``buffer``: Any object which exposes a buffer. When provided, ``initializer``
cannot be present (or has to be ``None``). The imported buffer may be
read-only or writable, depending on the object type.
New in version 2.3: optional ``buffer`` argument
New in version 3.4: allow initializer ``bytes`` or ``bytearray`` to set buffer directly
bitarray methods:
-----------------
``all()`` -> bool
Return True when all bits in bitarray are True.
Note that ``a.all()`` is faster than ``all(a)``.
``any()`` -> bool
Return True when any bit in bitarray is True.
Note that ``a.any()`` is faster than ``any(a)``.
``append(item, /)``
Append ``item`` to the end of the bitarray.
``buffer_info()`` -> tuple
Return a tuple containing:
0. memory address of buffer
1. buffer size (in bytes)
2. bit-endianness as a Unicode string
3. number of pad bits
4. allocated memory for the buffer (in bytes)
5. memory is read-only
6. buffer is imported
7. number of buffer exports
``bytereverse(start=0, stop=<end of buffer>, /)``
For each byte in byte-range(start, stop) reverse bits in-place.
The start and stop indices are given in terms of bytes (not bits).
Also note that this method only changes the buffer; it does not change the
bit-endianness of the bitarray object. Pad bits are left unchanged such
that two consecutive calls will always leave the bitarray unchanged.
New in version 2.2.5: optional start and stop arguments
``clear()``
Remove all items from the bitarray.
New in version 1.4
``copy()`` -> bitarray
Return a copy of the bitarray.
``count(value=1, start=0, stop=<end>, step=1, /)`` -> int
Number of occurrences of ``value`` bitarray within ``[start:stop:step]``.
Optional arguments ``start``, ``stop`` and ``step`` are interpreted in
slice notation, meaning ``a.count(value, start, stop, step)`` equals
``a[start:stop:step].count(value)``.
The ``value`` may also be a sub-bitarray. In this case non-overlapping
occurrences are counted within ``[start:stop]`` (``step`` must be 1).
New in version 1.1.0: optional start and stop arguments
New in version 2.3.7: optional step argument
New in version 2.9: add non-overlapping sub-bitarray count
``decode(code, /)`` -> iterator
Given a prefix code (a dict mapping symbols to bitarrays, or ``decodetree``
object), decode content of bitarray and return an iterator over
corresponding symbols.
See also: `Bitarray 3 transition <https://github.com/ilanschnell/bitarray/blob/master/doc/bitarray3.rst>`__
New in version 3.0: returns iterator (equivalent to past ``.iterdecode()``)
``encode(code, iterable, /)``
Given a prefix code (a dict mapping symbols to bitarrays),
iterate over the iterable object with symbols, and extend bitarray
with corresponding bitarray for each symbol.
``extend(iterable, /)``
Append items from to the end of the bitarray.
If ``iterable`` is a Unicode string, each ``0`` and ``1`` are appended as
bits (ignoring whitespace and underscore).
New in version 3.4: allow ``bytes`` object
``fill()`` -> int
Add zeros to the end of the bitarray, such that the length will be
a multiple of 8, and return the number of bits added [0..7].
``find(sub_bitarray, start=0, stop=<end>, /, right=False)`` -> int
Return lowest (or rightmost when ``right=True``) index where sub_bitarray
is found, such that sub_bitarray is contained within ``[start:stop]``.
Return -1 when sub_bitarray is not found.
New in version 2.1
New in version 2.9: add optional keyword argument ``right``
``frombytes(bytes, /)``
Extend bitarray with raw bytes from a bytes-like object.
Each added byte will add eight bits to the bitarray.
New in version 2.5.0: allow bytes-like argument
``fromfile(f, n=-1, /)``
Extend bitarray with up to ``n`` bytes read from file object ``f`` (or any
other binary stream what supports a ``.read()`` method, e.g. ``io.BytesIO``).
Each read byte will add eight bits to the bitarray. When ``n`` is omitted
or negative, reads and extends all data until EOF.
When ``n`` is non-negative but exceeds the available data, ``EOFError`` is
raised. However, the available data is still read and extended.
``index(sub_bitarray, start=0, stop=<end>, /, right=False)`` -> int
Return lowest (or rightmost when ``right=True``) index where sub_bitarray
is found, such that sub_bitarray is contained within ``[start:stop]``.
Raises ``ValueError`` when the sub_bitarray is not present.
New in version 2.9: add optional keyword argument ``right``
``insert(index, value, /)``
Insert ``value`` into bitarray before ``index``.
``invert(index=<all bits>, /)``
Invert all bits in bitarray (in-place).
When the optional ``index`` is given, only invert the single bit at index.
New in version 1.5.3: optional index argument
``pack(bytes, /)``
Extend bitarray from a bytes-like object, where each byte corresponds
to a single bit. The byte ``b'\x00'`` maps to bit 0 and all other bytes
map to bit 1.
This method, as well as the ``.unpack()`` method, are meant for efficient
transfer of data between bitarray objects to other Python objects (for
example NumPy's ndarray object) which have a different memory view.
New in version 2.5.0: allow bytes-like argument
``pop(index=-1, /)`` -> item
Remove and return item at ``index`` (default last).
Raises ``IndexError`` if index is out of range.
``remove(value, /)``
Remove the first occurrence of ``value``.
Raises ``ValueError`` if value is not present.
``reverse()``
Reverse all bits in bitarray (in-place).
``search(sub_bitarray, start=0, stop=<end>, /, right=False)`` -> iterator
Return iterator over indices where sub_bitarray is found, such that
sub_bitarray is contained within ``[start:stop]``.
The indices are iterated in ascending order (from lowest to highest),
unless ``right=True``, which will iterate in descending order (starting with
rightmost match).
See also: `Bitarray 3 transition <https://github.com/ilanschnell/bitarray/blob/master/doc/bitarray3.rst>`__
New in version 2.9: optional start and stop arguments - add optional keyword argument ``right``
New in version 3.0: returns iterator (equivalent to past ``.itersearch()``)
``setall(value, /)``
Set all elements in bitarray to ``value``.
Note that ``a.setall(value)`` is equivalent to ``a[:] = value``.
``sort(reverse=False)``
Sort all bits in bitarray (in-place).
``to01(group=0, sep=' ')`` -> str
Return bitarray as Unicode string of '0's and '1's.
The bits are grouped into ``group`` bits (default is no grouping).
When grouped, the string ``sep`` is inserted between groups
of ``group`` characters, default is a space.
New in version 3.3: optional ``group`` and ``sep`` arguments
``tobytes()`` -> bytes
Return the bitarray buffer in bytes (pad bits are set to zero).
``tofile(f, /)``
Write byte representation of bitarray to file object f.
``tolist()`` -> list
Return bitarray as list of integers.
``a.tolist()`` equals ``list(a)``.
Note that the list object being created will require 32 or 64 times more
memory (depending on the machine architecture) than the bitarray object,
which may cause a memory error if the bitarray is very large.
``unpack(zero=b'\x00', one=b'\x01')`` -> bytes
Return bytes that contain one byte for each bit in the bitarray,
using specified mapping.
bitarray data descriptors:
--------------------------
Data descriptors were added in version 2.6.
``endian`` -> str
bit-endianness as Unicode string
New in version 3.4: replaces former ``.endian()`` method
``nbytes`` -> int
buffer size in bytes
``padbits`` -> int
number of pad bits
``readonly`` -> bool
bool indicating whether buffer is read-only
Other objects:
--------------
``frozenbitarray(initializer=0, /, endian='big', buffer=None)`` -> frozenbitarray
Return a ``frozenbitarray`` object. Initialized the same way a ``bitarray``
object is initialized. A ``frozenbitarray`` is immutable and hashable,
and may therefore be used as a dictionary key.
New in version 1.1
``decodetree(code, /)`` -> decodetree
Given a prefix code (a dict mapping symbols to bitarrays),
create a binary tree object to be passed to ``.decode()``.
New in version 1.6
Functions defined in the `bitarray` module:
-------------------------------------------
``bits2bytes(n, /)`` -> int
Return the number of bytes necessary to store n bits.
``get_default_endian()`` -> str
Return the default bit-endianness for new bitarray objects being created.
Unless ``_set_default_endian('little')`` was called, the default
bit-endianness is ``big``.
New in version 1.3
``test(verbosity=1)`` -> TextTestResult
Run self-test, and return unittest.runner.TextTestResult object.
Functions defined in `bitarray.util` module:
--------------------------------------------
This sub-module was added in version 1.2.
``any_and(a, b, /)`` -> bool
Efficient implementation of ``any(a & b)``.
New in version 2.7
``ba2base(n, bitarray, /, group=0, sep=' ')`` -> str
Return a string containing the base ``n`` ASCII representation of
the bitarray. Allowed values for ``n`` are 2, 4, 8, 16, 32 and 64.
The bitarray has to be multiple of length 1, 2, 3, 4, 5 or 6 respectively.
For ``n=32`` the RFC 4648 Base32 alphabet is used, and for ``n=64`` the
standard base 64 alphabet is used.
When grouped, the string ``sep`` is inserted between groups
of ``group`` characters, default is a space.
See also: `Bitarray representations <https://github.com/ilanschnell/bitarray/blob/master/doc/represent.rst>`__
New in version 1.9
New in version 3.3: optional ``group`` and ``sep`` arguments
``ba2hex(bitarray, /, group=0, sep=' ')`` -> hexstr
Return a string containing the hexadecimal representation of
the bitarray (which has to be multiple of 4 in length).
When grouped, the string ``sep`` is inserted between groups
of ``group`` characters, default is a space.
New in version 3.3: optional ``group`` and ``sep`` arguments
``ba2int(bitarray, /, signed=False)`` -> int
Convert the given bitarray to an integer.
The bit-endianness of the bitarray is respected.
``signed`` indicates whether two's complement is used to represent the integer.
``base2ba(n, asciistr, /, endian=None)`` -> bitarray
Bitarray of base ``n`` ASCII representation.
Allowed values for ``n`` are 2, 4, 8, 16, 32 and 64.
For ``n=32`` the RFC 4648 Base32 alphabet is used, and for ``n=64`` the
standard base 64 alphabet is used. Whitespace is ignored.
See also: `Bitarray representations <https://github.com/ilanschnell/bitarray/blob/master/doc/represent.rst>`__
New in version 1.9
New in version 3.3: ignore whitespace
``byteswap(a, /, n=<buffer size>)``
Reverse every ``n`` consecutive bytes of ``a`` in-place.
By default, all bytes are reversed. Note that ``n`` is not limited to 2, 4
or 8, but can be any positive integer.
Also, ``a`` may be any object that exposes a writable buffer.
Nothing about this function is specific to bitarray objects.
New in version 3.4
``canonical_decode(bitarray, count, symbol, /)`` -> iterator
Decode bitarray using canonical Huffman decoding tables
where ``count`` is a sequence containing the number of symbols of each length
and ``symbol`` is a sequence of symbols in canonical order.
See also: `Canonical Huffman Coding <https://github.com/ilanschnell/bitarray/blob/master/doc/canonical.rst>`__
New in version 2.5
``canonical_huffman(dict, /)`` -> tuple
Given a frequency map, a dictionary mapping symbols to their frequency,
calculate the canonical Huffman code. Returns a tuple containing:
0. the canonical Huffman code as a dict mapping symbols to bitarrays
1. a list containing the number of symbols of each code length
2. a list of symbols in canonical order
Note: the two lists may be used as input for ``canonical_decode()``.
See also: `Canonical Huffman Coding <https://github.com/ilanschnell/bitarray/blob/master/doc/canonical.rst>`__
New in version 2.5
``correspond_all(a, b, /)`` -> tuple
Return tuple with counts of: ~a & ~b, ~a & b, a & ~b, a & b
New in version 3.4
``count_and(a, b, /)`` -> int
Return ``(a & b).count()`` in a memory efficient manner,
as no intermediate bitarray object gets created.
``count_n(a, n, value=1, /)`` -> int
Return lowest index ``i`` for which ``a[:i].count(value) == n``.
Raises ``ValueError`` when ``n`` exceeds total count (``a.count(value)``).
New in version 2.3.6: optional value argument
``count_or(a, b, /)`` -> int
Return ``(a | b).count()`` in a memory efficient manner,
as no intermediate bitarray object gets created.
``count_xor(a, b, /)`` -> int
Return ``(a ^ b).count()`` in a memory efficient manner,
as no intermediate bitarray object gets created.
This is also known as the Hamming distance.
``deserialize(bytes, /)`` -> bitarray
Return a bitarray given a bytes-like representation such as returned
by ``serialize()``.
See also: `Bitarray representations <https://github.com/ilanschnell/bitarray/blob/master/doc/represent.rst>`__
New in version 1.8
New in version 2.5.0: allow bytes-like argument
``hex2ba(hexstr, /, endian=None)`` -> bitarray
Bitarray of hexadecimal representation. hexstr may contain any number
(including odd numbers) of hex digits (upper or lower case).
Whitespace is ignored.
New in version 3.3: ignore whitespace
``huffman_code(dict, /, endian=None)`` -> dict
Given a frequency map, a dictionary mapping symbols to their frequency,
calculate the Huffman code, i.e. a dict mapping those symbols to
bitarrays (with given bit-endianness). Note that the symbols are not limited
to being strings. Symbols may be any hashable object.
``int2ba(int, /, length=None, endian=None, signed=False)`` -> bitarray
Convert the given integer to a bitarray (with given bit-endianness,
and no leading (big-endian) / trailing (little-endian) zeros), unless
the ``length`` of the bitarray is provided. An ``OverflowError`` is raised
if the integer is not representable with the given number of bits.
``signed`` determines whether two's complement is used to represent the integer,
and requires ``length`` to be provided.
``intervals(bitarray, /)`` -> iterator
Compute all uninterrupted intervals of 1s and 0s, and return an
iterator over tuples ``(value, start, stop)``. The intervals are guaranteed
to be in order, and their size is always non-zero (``stop - start > 0``).
New in version 2.7
``ones(n, /, endian=None)`` -> bitarray
Create a bitarray of length ``n``, with all values ``1``, and optional
bit-endianness (``little`` or ``big``).
New in version 2.9
``parity(a, /)`` -> int
Return parity of bitarray ``a``.
``parity(a)`` is equivalent to ``a.count() % 2`` but more efficient.
New in version 1.9
``pprint(bitarray, /, stream=None, group=8, indent=4, width=80)``
Prints the formatted representation of object on ``stream`` (which defaults
to ``sys.stdout``). By default, elements are grouped in bytes (8 elements),
and 8 bytes (64 elements) per line.
Non-bitarray objects are printed by the standard library
function ``pprint.pprint()``.
New in version 1.8
``random_k(n, /, k, endian=None)`` -> bitarray
Return (pseudo-) random bitarray of length ``n`` with ``k`` elements
set to one. Mathematically equivalent to setting (in a bitarray of
length ``n``) all bits at indices ``random.sample(range(n), k)`` to one.
The random bitarrays are reproducible when giving Python's ``random.seed()``
with a specific seed value.
This function requires Python 3.9 or higher, as it depends on the standard
library function ``random.randbytes()``. Raises ``NotImplementedError``
when Python version is too low.
New in version 3.6
``random_p(n, /, p=0.5, endian=None)`` -> bitarray
Return (pseudo-) random bitarray of length ``n``, where each bit has
probability ``p`` of being one (independent of any other bits). Mathematically
equivalent to ``bitarray((random() < p for _ in range(n)), endian)``, but much
faster for large ``n``. The random bitarrays are reproducible when giving
Python's ``random.seed()`` with a specific seed value.
This function requires Python 3.12 or higher, as it depends on the standard
library function ``random.binomialvariate()``. Raises ``NotImplementedError``
when Python version is too low.
See also: `Random Bitarrays <https://github.com/ilanschnell/bitarray/blob/master/doc/random_p.rst>`__
New in version 3.5
``sc_decode(stream)`` -> bitarray
Decompress binary stream (an integer iterator, or bytes-like object) of a
sparse compressed (``sc``) bitarray, and return the decoded bitarray.
This function consumes only one bitarray and leaves the remaining stream
untouched. Use ``sc_encode()`` for compressing (encoding).
See also: `Compression of sparse bitarrays <https://github.com/ilanschnell/bitarray/blob/master/doc/sparse_compression.rst>`__
New in version 2.7
``sc_encode(bitarray, /)`` -> bytes
Compress a sparse bitarray and return its binary representation.
This representation is useful for efficiently storing sparse bitarrays.
Use ``sc_decode()`` for decompressing (decoding).
See also: `Compression of sparse bitarrays <https://github.com/ilanschnell/bitarray/blob/master/doc/sparse_compression.rst>`__
New in version 2.7
``serialize(bitarray, /)`` -> bytes
Return a serialized representation of the bitarray, which may be passed to
``deserialize()``. It efficiently represents the bitarray object (including
its bit-endianness) and is guaranteed not to change in future releases.
See also: `Bitarray representations <https://github.com/ilanschnell/bitarray/blob/master/doc/represent.rst>`__
New in version 1.8
``strip(bitarray, /, mode='right')`` -> bitarray
Return a new bitarray with zeros stripped from left, right or both ends.
Allowed values for mode are the strings: ``left``, ``right``, ``both``
``subset(a, b, /)`` -> bool
Return ``True`` if bitarray ``a`` is a subset of bitarray ``b``.
``subset(a, b)`` is equivalent to ``a | b == b`` (and equally ``a & b == a``) but
more efficient as no intermediate bitarray object is created and the buffer
iteration is stopped as soon as one mismatch is found.
``sum_indices(a, /)`` -> int
Return sum of indices of all active bits in bitarray ``a``.
Equivalent to ``sum(i for i, v in enumerate(a) if v)``.
New in version 3.6
``urandom(n, /, endian=None)`` -> bitarray
Return random bitarray of length ``n`` (uses ``os.urandom()``).
New in version 1.7
``vl_decode(stream, /, endian=None)`` -> bitarray
Decode binary stream (an integer iterator, or bytes-like object), and
return the decoded bitarray. This function consumes only one bitarray and
leaves the remaining stream untouched. Use ``vl_encode()`` for encoding.
See also: `Variable length bitarray format <https://github.com/ilanschnell/bitarray/blob/master/doc/variable_length.rst>`__
New in version 2.2
``vl_encode(bitarray, /)`` -> bytes
Return variable length binary representation of bitarray.
This representation is useful for efficiently storing small bitarray
in a binary stream. Use ``vl_decode()`` for decoding.
See also: `Variable length bitarray format <https://github.com/ilanschnell/bitarray/blob/master/doc/variable_length.rst>`__
New in version 2.2
``xor_indices(a, /)`` -> int
Return xor reduced indices of all active bits in bitarray ``a``.
This is essentially equivalent to
``reduce(operator.xor, (i for i, v in enumerate(a) if v))``.
New in version 3.2
``zeros(n, /, endian=None)`` -> bitarray
Create a bitarray of length ``n``, with all values ``0``, and optional
bit-endianness (``little`` or ``big``).
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