CRC (Cyclic Redundancy Check) Library

7.1.0 · active · verified Sun Apr 12

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.

Warnings

breaking The `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.
breaking Python 3.7 support has been removed.
Fix: Upgrade your Python environment to version 3.8 or newer.
breaking The `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.
breaking The 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`.
gotcha The `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.

Install

pip install crc Install stable version

Imports

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.

Quickstart

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!")

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