https://github.com/ilanschnell/bitarray
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README.rst
bitarray: efficient arrays of booleans
======================================
This library provides an object type which efficiently represents an array
of booleans. Bitarrays are sequence types and behave very much like usual
lists. Eight bits are represented by one byte in a contiguous block of
memory. The user can select between two representations: little-endian
and big-endian. All functionality is implemented in C.
Methods for accessing the machine representation are provided, including the
ability to import and export buffers. This allows creating bitarrays that
are mapped to other objects, including memory-mapped files.
Roadmap
-------
In 2024 (probably around August), we are planning the release of bitarray 3.0.
The 3.0 release will:
* Remove Python 2.7 support.
* Rename ``.itersearch()`` to ``.search()`` and ``.iterdecode()``
to ``.decode()`` (and remove their non-iterator counterpart).
* Remove ``util.rindex()``, use ``.index(..., right=1)`` instead
* Remove ``util.make_endian()``, use ``bitarray(..., endian=...)`` instead
* Remove hackish support for ``bitarray()`` handling unpickling,
see detailed explaination in `#207 <https://github.com/ilanschnell/bitarray/pull/207>`__. This will close `#206 <https://github.com/ilanschnell/bitarray/issues/206>`__.
Key features
------------
* The bit-endianness can be specified for each bitarray object, see below.
* Sequence methods: slicing (including slice assignment and deletion),
operations ``+``, ``*``, ``+=``, ``*=``, the ``in`` operator, ``len()``
* Bitwise operations: ``~``, ``&``, ``|``, ``^``, ``<<``, ``>>`` (as well as
their in-place versions ``&=``, ``|=``, ``^=``, ``<<=``, ``>>=``).
* Fast methods for encoding and decoding variable bit length prefix codes.
* Bitarray objects support the buffer protocol (both importing and
exporting buffers).
* Packing and unpacking to other binary data formats, e.g. ``numpy.ndarray``.
* Pickling and unpickling of bitarray objects.
* Immutable ``frozenbitarray`` objects which are hashable
* Sequential search
* Type hinting
* Extensive test suite with about 500 unittests.
* Utility module ``bitarray.util``:
* conversion to and from hexadecimal strings
* (de-) serialization
* pretty printing
* conversion to and from integers
* creating Huffman codes
* compression of sparse bitarrays
* various count functions
* other helpful functions
Installation
------------
Python wheels are are available on PyPI for all mayor platforms and Python
versions. Which means you can simply:
.. code-block:: shell-session
$ pip install bitarray
In addition, conda packages are available (both the default Anaconda
repository as well as conda-forge support bitarray):
.. code-block:: shell-session
$ conda install bitarray
Once you have installed the package, you may want to test it:
.. code-block:: shell-session
$ python -c 'import bitarray; bitarray.test()'
bitarray is installed in: /Users/ilan/bitarray/bitarray
bitarray version: 2.9.2
sys.version: 3.10.14 (main, Oct 25 2022) [Clang 16.0.6]
sys.prefix: /Users/ilan/miniforge3
pointer size: 64 bit
sizeof(size_t): 8
sizeof(bitarrayobject): 80
HAVE_BUILTIN_BSWAP64: 1
default bit-endianness: big
machine byte-order: little
DEBUG: 0
.........................................................................
.........................................................................
................................................................
----------------------------------------------------------------------
Ran 502 tests in 0.187s
OK
The ``test()`` function is part of the API. It will return
a ``unittest.runner.TextTestResult`` object, such that one can verify that
all tests ran successfully by:
.. code-block:: python
import bitarray
assert bitarray.test().wasSuccessful()
Usage
-----
As mentioned above, bitarray objects behave very much like lists, so
there is not too much to learn. The biggest difference from list
objects (except that bitarray are obviously homogeneous) is the ability
to access the machine representation of the object.
When doing so, the bit-endianness is of importance; this issue is
explained in detail in the section below. Here, we demonstrate the
basic usage of bitarray objects:
.. code-block:: python
>>> from bitarray import bitarray
>>> a = bitarray() # create empty bitarray
>>> a.append(1)
>>> a.extend([1, 0])
>>> a
bitarray('110')
>>> x = bitarray(2 ** 20) # bitarray of length 1048576 (initialized to 0)
>>> len(x)
1048576
>>> bitarray('1001 011') # initialize from string (whitespace is ignored)
bitarray('1001011')
>>> lst = [1, 0, False, True, True]
>>> a = bitarray(lst) # initialize from iterable
>>> a
bitarray('10011')
>>> a[2] # indexing a single item will always return an integer
0
>>> a[2:4] # whereas indexing a slice will always return a bitarray
bitarray('01')
>>> a[2:3] # even when the slice length is just one
bitarray('0')
>>> a.count(1)
3
>>> a.remove(0) # removes first occurrence of 0
>>> a
bitarray('1011')
Like lists, bitarray objects support slice assignment and deletion:
.. code-block:: python
>>> a = bitarray(50)
>>> a.setall(0) # set all elements in a to 0
>>> a[11:37:3] = 9 * bitarray('1')
>>> a
bitarray('00000000000100100100100100100100100100000000000000')
>>> del a[12::3]
>>> a
bitarray('0000000000010101010101010101000000000')
>>> a[-6:] = bitarray('10011')
>>> a
bitarray('000000000001010101010101010100010011')
>>> a += bitarray('000111')
>>> a[9:]
bitarray('001010101010101010100010011000111')
In addition, slices can be assigned to booleans, which is easier (and
faster) than assigning to a bitarray in which all values are the same:
.. code-block:: python
>>> a = 20 * bitarray('0')
>>> a[1:15:3] = True
>>> a
bitarray('01001001001001000000')
This is easier and faster than:
.. code-block:: python
>>> a = 20 * bitarray('0')
>>> a[1:15:3] = 5 * bitarray('1')
>>> a
bitarray('01001001001001000000')
Note that in the latter we have to create a temporary bitarray whose length
must be known or calculated. Another example of assigning slices to Booleans,
is setting ranges:
.. code-block:: python
>>> a = bitarray(30)
>>> a[:] = 0 # set all elements to 0 - equivalent to a.setall(0)
>>> a[10:25] = 1 # set elements in range(10, 25) to 1
>>> a
bitarray('000000000011111111111111100000')
As of bitarray version 2.8, indices may also be lists of arbitrary
indices (like in NumPy), or bitarrays that are treated as masks,
see `Bitarray indexing <https://github.com/ilanschnell/bitarray/blob/master/doc/indexing.rst>`__.
Bitwise operators
-----------------
Bitarray objects support the bitwise operators ``~``, ``&``, ``|``, ``^``,
``<<``, ``>>`` (as well as their in-place versions ``&=``, ``|=``, ``^=``,
``<<=``, ``>>=``). The behavior is very much what one would expect:
.. code-block:: python
>>> a = bitarray('101110001')
>>> ~a # invert
bitarray('010001110')
>>> b = bitarray('111001011')
>>> a ^ b
bitarray('010111010')
>>> a &= b
>>> a
bitarray('101000001')
>>> a <<= 2 # in-place left shift by 2
>>> a
bitarray('100000100')
>>> b >> 1
bitarray('011100101')
The C language does not specify the behavior of negative shifts and
of left shifts larger or equal than the width of the promoted left operand.
The exact behavior is compiler/machine specific.
This Python bitarray library specifies the behavior as follows:
* the length of the bitarray is never changed by any shift operation
* blanks are filled by 0
* negative shifts raise ``ValueError``
* shifts larger or equal to the length of the bitarray result in
bitarrays with all values 0
It is worth noting that (regardless of bit-endianness) the bitarray left
shift (``<<``) always shifts towards lower indices, and the right
shift (``>>``) always shifts towards higher indices.
Bit-endianness
--------------
Unless explicitly converting to machine representation, using
the ``.tobytes()``, ``.frombytes()``, ``.tofile()`` and ``.fromfile()``
methods, as well as using ``memoryview``, the bit-endianness will have no
effect on any computation, and one can skip this section.
Since bitarrays allows addressing individual bits, where the machine
represents 8 bits in one byte, there are two obvious choices for this
mapping: little-endian and big-endian.
When dealing with the machine representation of bitarray objects, it is
recommended to always explicitly specify the endianness.
By default, bitarrays use big-endian representation:
.. code-block:: python
>>> a = bitarray()
>>> a.endian()
'big'
>>> a.frombytes(b'A')
>>> a
bitarray('01000001')
>>> a[6] = 1
>>> a.tobytes()
b'C'
Big-endian means that the most-significant bit comes first.
Here, ``a[0]`` is the lowest address (index) and most significant bit,
and ``a[7]`` is the highest address and least significant bit.
When creating a new bitarray object, the endianness can always be
specified explicitly:
.. code-block:: python
>>> a = bitarray(endian='little')
>>> a.frombytes(b'A')
>>> a
bitarray('10000010')
>>> a.endian()
'little'
Here, the low-bit comes first because little-endian means that increasing
numeric significance corresponds to an increasing address.
So ``a[0]`` is the lowest address and least significant bit,
and ``a[7]`` is the highest address and most significant bit.
The bit-endianness is a property of the bitarray object.
The endianness cannot be changed once a bitarray object is created.
When comparing bitarray objects, the endianness (and hence the machine
representation) is irrelevant; what matters is the mapping from indices
to bits:
.. code-block:: python
>>> bitarray('11001', endian='big') == bitarray('11001', endian='little')
True
Bitwise operations (``|``, ``^``, ``&=``, ``|=``, ``^=``, ``~``) are
implemented efficiently using the corresponding byte operations in C, i.e. the
operators act on the machine representation of the bitarray objects.
Therefore, it is not possible to perform bitwise operators on bitarrays
with different endianness.
When converting to and from machine representation, using
the ``.tobytes()``, ``.frombytes()``, ``.tofile()`` and ``.fromfile()``
methods, the endianness matters:
.. code-block:: python
>>> a = bitarray(endian='little')
>>> a.frombytes(b'\x01')
>>> a
bitarray('10000000')
>>> b = bitarray(endian='big')
>>> b.frombytes(b'\x80')
>>> b
bitarray('10000000')
>>> a == b
True
>>> a.tobytes() == b.tobytes()
False
As mentioned above, the endianness can not be changed once an object is
created. However, you can create a new bitarray with different endianness:
.. code-block:: python
>>> a = bitarray('111000', endian='little')
>>> b = bitarray(a, endian='big')
>>> b
bitarray('111000')
>>> a == b
True
Buffer protocol
---------------
Bitarray objects support the buffer protocol. They can both export their
own buffer, as well as import another object's buffer. To learn more about
this topic, please read `buffer protocol <https://github.com/ilanschnell/bitarray/blob/master/doc/buffer.rst>`__. There is also an example that shows how
to memory-map a file to a bitarray: `mmapped-file.py <https://github.com/ilanschnell/bitarray/blob/master/examples/mmapped-file.py>`__
Variable bit length prefix codes
--------------------------------
The ``.encode()`` method takes a dictionary mapping symbols to bitarrays
and an iterable, and extends the bitarray object with the encoded symbols
found while iterating. For example:
.. code-block:: python
>>> d = {'H':bitarray('111'), 'e':bitarray('0'),
... 'l':bitarray('110'), 'o':bitarray('10')}
...
>>> a = bitarray()
>>> a.encode(d, 'Hello')
>>> a
bitarray('111011011010')
Note that the string ``'Hello'`` is an iterable, but the symbols are not
limited to characters, in fact any immutable Python object can be a symbol.
Taking the same dictionary, we can apply the ``.decode()`` method which will
return a list of the symbols:
.. code-block:: python
>>> a.decode(d)
['H', 'e', 'l', 'l', 'o']
>>> ''.join(a.decode(d))
'Hello'
Since symbols are not limited to being characters, it is necessary to return
them as elements of a list, rather than simply returning the joined string.
The above dictionary ``d`` can be efficiently constructed using the function
``bitarray.util.huffman_code()``. I also wrote `Huffman coding in Python
using bitarray <http://ilan.schnell-web.net/prog/huffman/>`__ for more
background information.
When the codes are large, and you have many decode calls, most time will
be spent creating the (same) internal decode tree objects. In this case,
it will be much faster to create a ``decodetree`` object, which can be
passed to bitarray's ``.decode()`` and ``.iterdecode()`` methods, instead
of passing the prefix code dictionary to those methods itself:
.. code-block:: python
>>> from bitarray import bitarray, decodetree
>>> t = decodetree({'a': bitarray('0'), 'b': bitarray('1')})
>>> a = bitarray('0110')
>>> a.decode(t)
['a', 'b', 'b', 'a']
>>> ''.join(a.iterdecode(t))
'abba'
The sole purpose of the immutable ``decodetree`` object is to be passed
to bitarray's ``.decode()`` and ``.iterdecode()`` methods.
Frozenbitarrays
---------------
A ``frozenbitarray`` object is very similar to the bitarray object.
The difference is that this a ``frozenbitarray`` is immutable, and hashable,
and can therefore be used as a dictionary key:
.. code-block:: python
>>> from bitarray import frozenbitarray
>>> key = frozenbitarray('1100011')
>>> {key: 'some value'}
{frozenbitarray('1100011'): 'some value'}
>>> key[3] = 1
Traceback (most recent call last):
...
TypeError: frozenbitarray is immutable
Reference
=========
bitarray version: 2.9.2 -- `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 initial object, and endianness.
The initializer may be of the following types:
``int``: Create a bitarray of given integer length. The initial values are
all ``0``.
``str``: Create bitarray from a string of ``0`` and ``1``.
``iterable``: Create bitarray from iterable or sequence 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.
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 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
endianness of the bitarray object. Padbits 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, /)`` -> list
Given a prefix code (a dict mapping symbols to bitarrays, or ``decodetree``
object), decode content of bitarray and return it as a list of symbols.
``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.
``endian()`` -> str
Return the bit-endianness of the bitarray as a string (``little`` or ``big``).
``extend(iterable, /)``
Append all items from ``iterable`` to the end of the bitarray.
If the iterable is a string, each ``0`` and ``1`` are appended as
bits (ignoring whitespace and underscore).
``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, all bytes until EOF are read. When ``n`` is non-negative but
exceeds the data available, ``EOFError`` is raised (but the available data
is still read and appended).
``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.
``iterdecode(code, /)`` -> iterator
Given a prefix code (a dict mapping symbols to bitarrays, or ``decodetree``
object), decode content of bitarray and return an iterator over
the symbols.
``itersearch(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 oder (starting with
rightmost match).
New in version 2.9: optional start and stop arguments - add optional keyword argument ``right``.
``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, limit=<none>, /)`` -> list
Searches for given sub_bitarray in self, and return list of start
positions.
The optional argument limits the number of search results to the integer
specified. By default, all search results are returned.
``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()`` -> str
Return a string containing '0's and '1's, representing the bits in the
bitarray.
``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 integer items.
``a.tolist()`` is equal to ``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 containing one character for each bit in the bitarray,
using specified mapping.
bitarray data descriptors:
--------------------------
Data descriptors were added in version 2.6.
``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()`` or ``.iterdecode()``.
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 endianness for new bitarray objects being created.
Unless ``_set_default_endian('little')`` was called, the default 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.
``zeros(length, /, endian=None)`` -> bitarray
Create a bitarray of length, with all values 0, and optional
endianness, which may be 'big', 'little'.
``ones(length, /, endian=None)`` -> bitarray
Create a bitarray of length, with all values 1, and optional
endianness, which may be 'big', 'little'.
New in version 2.9.
``urandom(length, /, endian=None)`` -> bitarray
Return a bitarray of ``length`` random bits (uses ``os.urandom``).
New in version 1.7.
``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.
``make_endian(bitarray, /, endian)`` -> bitarray
When the endianness of the given bitarray is different from ``endian``,
return a new bitarray, with endianness ``endian`` and the same elements
as the original bitarray.
Otherwise (endianness is already ``endian``) the original bitarray is returned
unchanged.
New in version 1.3.
New in version 2.9: deprecated - use ``bitarray()``.
``rindex(bitarray, sub_bitarray=1, start=0, stop=<end>, /)`` -> int
Return rightmost (highest) index where sub_bitarray (or item - defaults
to 1) is found in bitarray (``a``), such that sub_bitarray is contained
within ``a[start:stop]``.
Raises ``ValueError`` when the sub_bitarray is not present.
New in version 2.3.0: optional start and stop arguments.
New in version 2.9: deprecated - use ``.index(..., right=1)``.
``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``
``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.
``parity(a, /)`` -> int
Return parity of bitarray ``a``.
``parity(a)`` is equivalent to ``a.count() % 2`` but more efficient.
New in version 1.9.
``count_and(a, b, /)`` -> int
Return ``(a & b).count()`` in a memory efficient manner,
as no intermediate bitarray object gets created.
``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.
``any_and(a, b, /)`` -> bool
Efficient implementation of ``any(a & b)``.
New in version 2.7.
``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.
``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.
``ba2hex(bitarray, /)`` -> hexstr
Return a string containing the hexadecimal representation of
the bitarray (which has to be multiple of 4 in length).
``hex2ba(hexstr, /, endian=None)`` -> bitarray
Bitarray of hexadecimal representation. hexstr may contain any number
(including odd numbers) of hex digits (upper or lower case).
``ba2base(n, bitarray, /)`` -> 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.
See also: `Bitarray representations <https://github.com/ilanschnell/bitarray/blob/master/doc/represent.rst>`__
New in version 1.9.
``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.
See also: `Bitarray representations <https://github.com/ilanschnell/bitarray/blob/master/doc/represent.rst>`__
New in version 1.9.
``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.
``int2ba(int, /, length=None, endian=None, signed=False)`` -> bitarray
Convert the given integer to a bitarray (with given 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.
``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.
``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.
``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.
``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.
``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.
``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.
``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 endianness). Note that the symbols are not limited
to being strings. Symbols may may be any hashable object (such as ``None``).
``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.
``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.
