TheAlgorithms/Python · error · ValueError

size of parity don't match with size of data

Error message

size of parity don't match with size of data

What it means

Thrown by emitter_converter() in the Hamming code module when the number of parity bits (size_par) does not fit the data length. The guard raises when size_par + len(data) <= 2**size_par - (len(data) - 1), i.e. when the parity count is inconsistent with the payload: for a 12-bit data string, size_par=4 works (16 total bits) but size_par=5 raises because the parity scheme would produce a mismatched codeword layout.

Source

Thrown at hashes/hamming_code.py:86

# Functions of hamming code-------------------------------------------
def emitter_converter(size_par, data):
    """
    :param size_par: how many parity bits the message must have
    :param data:  information bits
    :return: message to be transmitted by unreliable medium
            - bits of information merged with parity bits

    >>> emitter_converter(4, "101010111111")
    ['1', '1', '1', '1', '0', '1', '0', '0', '1', '0', '1', '1', '1', '1', '1', '1']
    >>> emitter_converter(5, "101010111111")
    Traceback (most recent call last):
        ...
    ValueError: size of parity don't match with size of data
    """
    if size_par + len(data) <= 2**size_par - (len(data) - 1):
        raise ValueError("size of parity don't match with size of data")

    data_out = []
    parity = []
    bin_pos = [bin(x)[2:] for x in range(1, size_par + len(data) + 1)]

    # sorted information data for the size of the output data
    data_ord = []
    # data position template + parity
    data_out_gab = []
    # parity bit counter
    qtd_bp = 0
    # counter position of data bits
    cont_data = 0

    for x in range(1, size_par + len(data) + 1):
        # Performs a template of bit positions - who should be given,
        # and who should be parity
        if qtd_bp < size_par:

View on GitHub (pinned to f5988cc097)

Solutions

1. Match size_par to the data length: for 12 data bits use size_par=4 (2**4 = 16 >= 4 + 12).
2. Compute size_par programmatically: smallest p such that 2**p >= p + len(data) + 1, then verify against the guard's condition before calling.
3. Keep (size_par, data length) as one configuration unit so they are never changed independently.

Example fix

# before
emitter_converter(5, "101010111111")  # ValueError

# after
import math
def parity_size(n_data: int) -> int:
    return next(p for p in range(1, 17) if 2**p >= p + n_data + 1)
emitter_converter(parity_size(len(data)), data)

def parity_size(n_data: int) -> int:
    return next(p for p in range(1, 17) if 2**p >= p + n_data + 1)

size_par = parity_size(len(data))

def is_valid_hamming_config(size_par: int, data: str) -> bool:
    return size_par > 0 and not (size_par + len(data) <= 2**size_par - (len(data) - 1))

try:
    codeword = emitter_converter(size_par, data)
except ValueError as e:
    raise ValueError(
        f"parity size {size_par} invalid for {len(data)}-bit payload"
    ) from e

When it happens

Trigger: Calling emitter_converter(5, "101010111111") raises; emitter_converter(4, "101010111111") succeeds. Also triggered when data length changes (shorter/longer bit string) while size_par is kept fixed from a previous configuration.

Common situations: Hardcoding the parity size from an example while feeding different payload lengths; porting code where the data word size changed; generating test vectors with arbitrary (size_par, data) pairs.

Related errors

• number must be positive
• The value of input must be non-negative
• Shift must be non-negative
• Input value must be a 'int' type
• the value of both inputs must be positive

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/43af3ce45688bad4. Report an issue: GitHub.