crc

library8.0.0pypypi✓ verified 23d ago

The `crc` library provides pure Python implementations for calculating, verifying, and configuring Cyclic Redundancy Check (CRC) checksums. It supports various predefined CRC configurations (e.g., CRC8, CRC16, CRC32, CRC64) and allows for custom configurations. Currently at version 7.1.0, the library is actively maintained with regular releases, often including new CRC configurations and bug fixes, and requires Python >=3.8 and <4.0.

serialization

pip install crc

github ↗package ↗homepage ↗docs ↗changelog ↗

INSTALL

IMPORT

SIG · CRC

crc

serializationpythonv8.0.0

Install

1.5s avg

Import

47ms

Disk

16MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v7.1.0 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 0.050s · 17.8MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 1.5s · import 0.044s · 18MB

16MB installed

● package 16MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

Calculator

✓ from crc import Calculator

Introduced in version 5.0.0 after the package structure changed.

Crc8

✓ from crc import Crc8

Introduced in version 5.0.0 after the package structure changed.

Crc16

✓ from crc import Crc16

Introduced in version 5.0.0 after the package structure changed.

Configuration

✓ from crc import Configuration

Introduced in version 5.0.0 after the package structure changed, used for custom CRC setups.

Calculates the CRC-8 CCITT checksum for a sample byte sequence and verifies it. This demonstrates the basic usage of a predefined CRC configuration.

from crc import Calculator, Crc8 data = bytes([0, 1, 2, 3, 4, 5]) # Create a calculator with a predefined configuration (e.g., CRC-8 CCITT) calculator = Calculator(Crc8.CCITT) # Calculate the checksum checksum = calculator.checksum(data) print(f"CRC-8 CCITT checksum: {checksum:#04x}") # Verify the checksum assert calculator.verify(data, 0xBC) print("Checksum verified successfully!")

Debug

Known issues

breakingThe `Crc16.CCITT` configuration was renamed to `Crc16.XMODEM`. The new `Crc16.KERMIT` configuration now provides the 'official' CCITT parameters.

fix

Replace `Crc16.CCITT` with `Crc16.XMODEM` if you relied on the previous values, or with `Crc16.KERMIT` for the new official CCITT parameters.

affects: >=7.0.0

breakingPython 3.7 support has been removed.

fix

Upgrade your Python environment to version 3.8 or newer.

affects: >=6.0.0

breakingThe `SAEJ1850` configuration was adjusted to match the official specification. For users relying on the previously misconfigured values, a new configuration named `SAE_J1850_ZERO` was added.

fix

If your application depends on the original (pre-6.0.0) `SAEJ1850` values, switch to `SAE_J1850_ZERO`. Otherwise, continue using `SAEJ1850` for the corrected specification.

affects: >=6.0.0

breakingThe library transitioned from a single-file module (`crc.py`) to an src-based package layout. Direct imports that assumed a single `crc.py` file will no longer work.

fix

Ensure all imports follow standard package patterns, e.g., `from crc import Calculator, Crc8`.

affects: >=5.0.0

gotchaThe `digest` function had unstable return values, particularly in configurations that required reverse output and when the CRC register was manually manipulated. Standard `Calculator` usage was generally unaffected.

fix

Upgrade to version 6.1.2 or newer to resolve this issue. In older affected versions, avoid manual manipulation of CRC registers if relying on reverse output configurations.

affects: <6.1.2

Errors

Common errors & fixes

ModuleNotFoundError: No module named 'crc'

The 'crc' library has not been installed in your Python environment or the Python interpreter cannot find it.

fix

Run `pip install crc` to install the library.

TypeError: a bytes-like object is required, not 'str'

CRC calculation functions typically expect binary data (bytes) as input, but a string (str) was provided.

fix

Encode the string to bytes before passing it to the checksum method, e.g., `data.encode('utf-8')`.

AttributeError: 'Configuration' object has no attribute 'checksum'

You are attempting to call the `checksum` method directly on a CRC configuration object (e.g., `Crc8.CCITT`), which only defines the CRC parameters, not the calculation method. The calculation method belongs to a `Calculator` instance.

fix

First, create a `Calculator` instance with the desired configuration, then call `checksum` on the calculator, e.g., `calculator = Calculator(Crc8.CCITT)` and then `calculator.checksum(data)`.

Upgrade

Version history

8.0.0latest on PyPI · released Aug 29, 2026

Audit

Dependencies

pythonrequiredRequires Python 3.8 or newer, but not Python 4.

Agent activity

16 hits · last 30 days

node

Resources

githubhttps://github.com/Nicoretti/crc ↗

packagehttps://pypi.org/project/crc/ ↗

homepagehttps://nicoretti.github.io/crc/ ↗

docshttps://nicoretti.github.io/crc/ ↗

changeloghttps://nicoretti.github.io/crc/changelog/unreleased/ ↗