arithmetipy 0.3.0

Python bindings for a Rust implementation of arithmetic coding (encoder/decoder).

Arithmetipy

Python bindings for a Rust implementation of arithmetic coding.
This library provides streaming arithmetic encoder and decoder with 32-bit precision.
It’s built in Rust for speed, exposed to Python via PyO3 and [maturin]

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Installation

pip install arithmetipy

Develop

pip install maturin
git clone https://github.com/khoda81/arithmetipy
cd arithmetipy
maturin develop

Usage

from arithmetipy import ArithmeticEncoder, ArithmeticDecoder

# Our "alphabet" is integers {0, 1, 2}
alphabet_size = 3
seq = [0, 1, 2, 1, 1, 0, 1, 2]

# --- Encode ---
encoder = ArithmeticEncoder()
for symbol in seq:
    # here: (start, end, denominator)
    encoder.encode(symbol, symbol + 1, alphabet_size)

encoded = encoder.read()
print("Encoded bytes:", encoded)

# --- Decode ---
decoder = ArithmeticDecoder(encoded)
# All symbols have uniform weight
weights = [1] * alphabet_size
out = [decoder.decode_next(weights) for _ in seq]
print("Decoded symbols:", out)

assert out == seq

Output:

Encoded bytes: b'3\xd4'
Decoded symbols: [0, 1, 2, 1, 1, 0, 1, 2]

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API

ArithmeticEncoder

• encode(start: int, end: int, denominator: int) -> None Encode a symbol interval.
• read() -> bytes Get the encoded byte stream and reset the internal buffer.

ArithmeticDecoder

• __init__(data: bytes) Create a decoder from an encoded byte stream.
• decode_next(weights: List[int]) -> int Decode the next symbol given its weights (probability distribution).