TheAlgorithms/Python · error · ValueError

Invalid IPv4 address format

Error message

Invalid IPv4 address format

What it means

Raised by ipv4_to_decimal(ipv4_address) in conversions/ipv4_conversion.py:30 when splitting the address on '.' does not yield exactly 4 octets. The function is strict about dotted-quad shape: too few parts ('10.0.255'), too many ('10.0.0.1.5'), or a missing/wrong separator all produce ValueError('Invalid IPv4 address format'). Note each part must also parse with int(), so non-numeric parts raise int's own ValueError first.

Source

Thrown at conversions/ipv4_conversion.py:30

        int: The decimal representation of the IP address.

    >>> ipv4_to_decimal("192.168.0.1")
    3232235521
    >>> ipv4_to_decimal("10.0.0.255")
    167772415
    >>> ipv4_to_decimal("10.0.255")
    Traceback (most recent call last):
        ...
    ValueError: Invalid IPv4 address format
    >>> ipv4_to_decimal("10.0.0.256")
    Traceback (most recent call last):
        ...
    ValueError: Invalid IPv4 octet 256
    """

    octets = [int(octet) for octet in ipv4_address.split(".")]
    if len(octets) != 4:
        raise ValueError("Invalid IPv4 address format")

    decimal_ipv4 = 0
    for octet in octets:
        if not 0 <= octet <= 255:
            raise ValueError(f"Invalid IPv4 octet {octet}")  # noqa: EM102
        decimal_ipv4 = (decimal_ipv4 << 8) + int(octet)

    return decimal_ipv4


def alt_ipv4_to_decimal(ipv4_address: str) -> int:
    """
    >>> alt_ipv4_to_decimal("192.168.0.1")
    3232235521
    >>> alt_ipv4_to_decimal("10.0.0.255")
    167772415
    """
    return int("0x" + "".join(f"{int(i):02x}" for i in ipv4_address.split(".")), 16)

View on GitHub (pinned to f5988cc097)

Solutions

1. Strip CIDR/port decorations first: ipv4 = addr.split('/')[0].rsplit(':', 1)[0]
2. Validate shape before calling: len(addr.split('.')) == 4 and each part is decimal 0-255 (or use ipaddress.IPv4Address)
3. Route IPv6 through ipaddress.IPv6Address instead of this function

Example fix

# before
ipv4_to_decimal('192.168.0.1/24')  # ValueError

# after
import ipaddress
ipv4_to_decimal(str(ipaddress.ip_interface('192.168.0.1/24').ip))

import ipaddress
try:
    ipaddress.IPv4Address(ipv4_address)
except ipaddress.AddressValueError as e:
    raise ValueError(f'not a plain IPv4 address: {ipv4_address!r}') from e

try:
    ipv4_to_decimal(ipv4_address)
except ValueError as e:
    raise ValueError(f'bad address {ipv4_address!r}: {e}') from e

When it happens

Trigger: ipv4_to_decimal('10.0.255'), ipv4_to_decimal('10.0.0.1.5'), ipv4_to_decimal('192.168.0.1/24') (CIDR suffix becomes a 5th part), or addresses built by joining the wrong list length.

Common situations: Passing CIDR notation or addresses with port ('1.2.3.4:80'); constructing IPs from split() output without rechecking part count; trailing dots; IPv6 strings reaching an IPv4-only function.

Related errors

• Invalid IPv4 octet {octet}
• Invalid decimal IPv4 address
• base must be >= 2
• Input value is not an integer
• Incorrect 'from_type' or 'to_type' value: {from_type!r}, {to

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/2f51a6423feb9c9b. Report an issue: GitHub.