bitlist

Pure-Python library for working with bit vectors.

Purpose

This library allows programmers to work with bit vectors using a pure-Python data structure. Its design prioritizes interoperability with built-in Python classes and operators.

Installation and Usage

This library is available as a package on PyPI:

python -m pip install bitlist

The library can be imported in the usual way:

import bitlist
from bitlist import bitlist

Examples

This library makes it possible to construct bit vectors from a variety of representations (including integers, bytes-like objects, strings of binary digits, lists of binary digits, and other bit vectors). Integer arguments are converted into a big-endian binary representation:

>>> bitlist(123)
bitlist('1111011')
>>> bitlist(bytes([255, 254]))
bitlist('1111111111111110')
>>> bitlist('101')
bitlist('101')
>>> bitlist([1, 0, 1, 1])
bitlist('1011')
>>> bitlist(bitlist('1010'))
bitlist('1010')

The optional length parameter can be used to specify the length of the created bit vector (padding consisting of zero bits is applied automatically on the left-hand size, if necessary):

>>> bitlist(bytes([123]), length=16)
bitlist('0000000001111011')
>>> bitlist(16, 64)
bitlist('0000000000000000000000000000000000000000000000000000000000010000')
>>> bitlist(bitlist(123), 8)
bitlist('01111011')

If the length parameter has a value that is less than the minimum number of bits that would be included according to the default constructor behaviors, the bit vector is truncated on the left-hand side to match the specified length:

>>> bitlist(bytes([123]), length=7)
bitlist('1111011')
>>> bitlist(bytes([123]), 4)
bitlist('1011')
>>> bitlist(bytes([123]), 2)
bitlist('11')
>>> bitlist(bytes([123]), 0)
bitlist()

Bit vectors are iterable sequences of individual bits (where each bit is represented as an integer). Both slice notation and retrieval of individual bits by index are supported. Furthermore, methods are available for converting a bit vector into other common representations:

>>> b = bitlist('1111011')
>>> b[1:-1]
bitlist('11101')
>>> b[0]
1
>>> [bit for bit in b]
[1, 1, 1, 1, 0, 1, 1]
>>> b.bin()
'1111011'
>>> b.hex()
'7b'
>>> list(b.to_bytes())
[123]

Concatenation, partitioning, subscription and slicing, shift and rotation, comparison, and logical operations are also supported by instances of the bitlist class. The larger example below -- a bitwise addition function -- illustrates the use of various operators supported by instances of the bitlist class:

>>> def add(x, y):
...     """Bitwise addition algorithm."""
...     r = bitlist(0)
...     carry = 0
...     # Use negative indices for big-endian interface.
...     for i in range(1, max(len(x), len(y)) + 1):
...         r[-i] = (x[-i] ^ y[-i]) ^ carry
...         carry = (x[-i] & y[-i]) | (x[-i] & carry) | (y[-i] & carry)
...     r[-(max(len(x), len(y)) + 1)] = carry
...     return r
...
>>> int(add(bitlist(123), bitlist(456)))
579

The testing script that accompanies this library contains additional examples of bitwise arithmetic operations implemented with the help of bitlist operators.

Development

All installation and development dependencies are fully specified in pyproject.toml. The project.optional-dependencies object is used to specify optional requirements for various development tasks. This makes it possible to specify additional options (such as docs, lint, and so on) when performing installation using pip:

python -m pip install .[docs,lint]

Documentation

The documentation can be generated automatically from the source files using Sphinx:

python -m pip install .[docs]
cd docs
sphinx-apidoc -f -E --templatedir=_templates -o _source .. && make html

Testing and Conventions

All unit tests are executed and their coverage is measured when using pytest (see the pyproject.toml file for configuration details):

python -m pip install .[test]
python -m pytest

The subset of the unit tests included in the module itself and the documentation examples that appear in the testing script can be executed separately using doctest:

python src/bitlist/bitlist.py -v
python test/test_bitlist.py -v

Style conventions are enforced using Pylint:

python -m pip install .[lint]
python -m pylint src/bitlist test/test_bitlist.py

Contributions

In order to contribute to the source code, open an issue or submit a pull request on the GitHub page for this library.

Versioning

Beginning with version 0.3.0, the version number format for this library and the changes to the library associated with version number increments conform with Semantic Versioning 2.0.0.

Publishing

This library can be published as a package on PyPI by a package maintainer. First, install the dependencies required for packaging and publishing:

python -m pip install .[publish]

Ensure that the correct version number appears in pyproject.toml, and that any links in this README document to the Read the Docs documentation of this package (or its dependencies) have appropriate version numbers. Also ensure that the Read the Docs project for this library has an automation rule that activates and sets as the default all tagged versions. Create and push a tag for this version (replacing ?.?.? with the version number):

git tag ?.?.?
git push origin ?.?.?

Remove any old build/distribution files. Then, package the source into a distribution archive:

rm -rf build dist src/*.egg-info
python -m build --sdist --wheel .

Finally, upload the package distribution archive to PyPI:

python -m twine upload dist/*

lapets/bitlist