bitstruct
This module performs conversions between Python values and C bit field structs represented as Python byte strings.
Decision gist · record as of 2026-08-14
Yes, if you need to work with bit-level binary data. Bitstruct is stable (Production/Stable status), actively maintained, has no dependencies, and provides a clear interface for a specialized but real problem. The optional C acceleration and wide platform support make it practical for both development and performance-critical code. No security vulnerabilities reported.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.9 or later.
- C implementation available only on CPython 3 and must be explicitly imported; pure Python fallback is default.
- Medium install friction due to compiled C extensions for multiple platforms (wheels provided for CPython 3.10–3.11 across Linux, macOS, Windows, and ARM architectures).
License · maintenance · safety
MIT (permissive) — MIT license permits unrestricted use, modification, and distribution in both open and closed-source projects with minimal attribution requirements.
last release 2026-02-17 (178 days) · last repo commit 2026-02-17 · 135 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 5,110,055 downloads/mo, #2,167 on PyPI
Alternatives
Verify before relying
pip install bitstruct
from bitstruct import pack, unpack
packed = pack('u1u3u4s16', 1, 2, 3, -4)
print(packed) # b'\xa3\xff\xfc'
unpacked = unpack('u1u3u4s16', packed)
print(unpacked) # (1, 2, 3, -4)- Whether the C implementation is automatically selected or requires explicit import on supported platforms
- Performance characteristics and speedup magnitude of C vs. pure Python implementation for typical workloads
- Compatibility with Python 3.12+ beyond the stated 3.9+ requirement
What it is and what it does
Bitstruct converts between Python values and bit-level binary structures, extending the interface of Python's built-in struct module to work on individual bits instead of bytes. It provides functions to pack values into compact binary representations and unpack them back, with support for unsigned integers, signed integers, floats, booleans, raw bytes, and text strings at arbitrary bit boundaries.
Format strings specify bit widths and types (e.g., 'u1u3u4s16' for a 1-bit unsigned, 3-bit unsigned, 4-bit unsigned, and 16-bit signed integer), and compiled format objects allow reuse of the same specification across multiple operations. It supports bit-offset packing into existing buffers, dictionary-based packing/unpacking, and byte-order control. The library includes both a pure Python implementation and optional C accelerations for faster pack/unpack operations on CPython 3.
Use it for
- Parse binary network protocols or file formats with non-byte-aligned fields (e.g., bit flags, variable-width integers)
- Serialize structured data into compact binary representations for embedded systems or bandwidth-constrained communication
- Extract and manipulate individual bit fields from hardware register dumps or low-level binary data
- Implement bit-level codecs for compression or encoding schemes that operate below byte boundaries
- Test and validate binary protocol implementations by packing/unpacking known test vectors
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, if you need to work with bit-level binary data.
Bitstruct is stable (Production/Stable status), actively maintained, has no dependencies, and provides a clear interface for a specialized but real problem. The optional C acceleration and wide platform support make it practical for both development and performance-critical code. No security vulnerabilities reported.
Install
bitstruct on PyPI
Before you install
Medium install friction due to compiled C extensions for multiple platforms (wheels provided for CPython 3.10–3.11 across Linux, macOS, Windows, and ARM architectures). Active maintenance with recent releases; no runtime dependencies.
Requires Python 3.9 or later. C implementation available only on CPython 3 and must be explicitly imported; pure Python fallback is default.
License in practice
MIT license permits unrestricted use, modification, and distribution in both open and closed-source projects with minimal attribution requirements.
Quickstart
pip install bitstruct
from bitstruct import pack, unpack
packed = pack('u1u3u4s16', 1, 2, 3, -4)
print(packed) # b'\xa3\xff\xfc'
unpacked = unpack('u1u3u4s16', packed)
print(unpacked) # (1, 2, 3, -4)Verify before relying
- Whether the C implementation is automatically selected or requires explicit import on supported platforms
- Performance characteristics and speedup magnitude of C vs. pure Python implementation for typical workloads
- Compatibility with Python 3.12+ beyond the stated 3.9+ requirement
Package facts
| License | MIT permissive |
| Python support | Supports the current Python release >=3.9 |
| Install friction | Medium. Platform-specific wheel |
| Runtime dependencies | None |
| Maintenance | Actively maintained 178 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 5,110,055 / month, #2,167 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableProgramming Language :: PythonProgramming Language :: Python :: 3Programming Language :: Python :: Implementation :: CPython |
Evidence: bitstruct-8.22.1-cp310-cp310-macosx_10_9_x86_64.whl; bitstruct-8.22.1-cp310-cp310-macosx_11_0_arm64.whl; bitstruct-8.22.1-cp310-cp310-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl; bitstruct-8.22.1-cp310-cp310-manylinux2014_armv7l.manylinux_2_17_armv7l.manylinux_2_31_armv7l.whl; bitstruct-8.22.1-cp310-cp310-manylinux2014_x86_64.manylinux_2_17_x86_64.manylinux_2_28_x86_64.whl; bitstruct-8.22.1-cp310-cp310-musllinux_1_2_aarch64.whl; bitstruct-8.22.1-cp310-cp310-musllinux_1_2_armv7l.whl; bitstruct-8.22.1-cp310-cp310-musllinux_1_2_x86_64.whl; bitstruct-8.22.1-cp310-cp310-win32.whl; bitstruct-8.22.1-cp310-cp310-win_amd64.whl; bitstruct-8.22.1-cp310-cp310-win_arm64.whl; bitstruct-8.22.1-cp311-cp311-macosx_10_9_x86_64.whl; bitstruct-8.22.1-cp311-cp311-macosx_11_0_arm64.whl; bitstruct-8.22.1-cp311-cp311-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl; bitstruct-8.22.1-cp311-cp311-manylinux2014_armv7l.manylinux_2_17_armv7l.manylinux_2_31_armv7l.whl; bitstruct-8.22.1-cp311-cp311-manylinux2014_x86_64.manylinux_2_17_x86_64.manylinux_2_28_x86_64.whl; bitstruct-8.22.1-cp311-cp311-musllinux_1_2_aarch64.whl; bitstruct-8.22.1-cp311-cp311-musllinux_1_2_armv7l.whl; bitstruct-8.22.1-cp311-cp311-musllinux_1_2_x86_64.whl; bitstruct-8.22.1-cp311-cp311-win32.whl
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See also bitstring · cbitstruct · plum-py · dissect.cstruct · kaitaistruct · tibs · construct-classes · msgpack · bitarray-hardbyte · fdt