TheAlgorithms/Python · error · ValueError

Invalid decimal IPv4 address

Error message

Invalid decimal IPv4 address

What it means

Raised by decimal_to_ipv4(decimal_ipv4) in conversions/ipv4_conversion.py:72 when the integer is outside 0..4294967295 (2**32 - 1). An IPv4 address is exactly 32 bits; negative numbers or values above the unsigned 32-bit maximum cannot map to one, so the function raises ValueError('Invalid decimal IPv4 address') before extracting octets.

Source

Thrown at conversions/ipv4_conversion.py:72

    Args:
        decimal_ipv4: An integer representing the decimal IP address.

    Returns:
        The IPv4 representation of the decimal IP address.

    >>> decimal_to_ipv4(3232235521)
    '192.168.0.1'
    >>> decimal_to_ipv4(167772415)
    '10.0.0.255'
    >>> decimal_to_ipv4(-1)
    Traceback (most recent call last):
        ...
    ValueError: Invalid decimal IPv4 address
    """

    if not (0 <= decimal_ipv4 <= 4294967295):
        raise ValueError("Invalid decimal IPv4 address")

    ip_parts = []
    for _ in range(4):
        ip_parts.append(str(decimal_ipv4 & 255))
        decimal_ipv4 >>= 8

    return ".".join(reversed(ip_parts))


if __name__ == "__main__":
    import doctest

    doctest.testmod()

View on GitHub (pinned to f5988cc097)

Solutions

1. Mask to 32 bits before calling: decimal_to_ipv4(value & 0xFFFFFFFF) when wrapping is the intended semantics
2. Unpack network words as unsigned: struct.unpack('<I', data) rather than '<i'
3. Range-check at your boundary: if not 0 <= value <= 4294967295: reject

Example fix

# before
signed, = struct.unpack('<i', word)
decimal_to_ipv4(signed)  # negative -> ValueError

# after
unsigned, = struct.unpack('<I', word)
decimal_to_ipv4(unsigned)

if not 0 <= decimal_ipv4 <= 0xFFFFFFFF:
    raise ValueError(f'{decimal_ipv4} is not an unsigned 32-bit value')

def is_u32(v: object) -> TypeGuard[int]:
    return isinstance(v, int) and 0 <= v <= 0xFFFFFFFF

When it happens

Trigger: decimal_to_ipv4(-1), decimal_to_ipv4(2**32), or decimal values produced by signed 32-bit arithmetic, struct unpacking with signed formats, or unchecked increments.

Common situations: Reading 32-bit words unpacked as signed integers ('<i' instead of '<I'); converting hash/CRC values that exceed 2**32; off-by-one loop bounds when enumerating address ranges.

Related errors

• Invalid IPv4 octet {octet}
• Invalid IPv4 address format
• base must be >= 2
• base must be <= 36
• No input value was provided

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/a6fa64f86f1ac632. Report an issue: GitHub.