import socket

def int16(x):
    x = int(x)
    return x.to_bytes(2, 'big')


def int24(x):
    x = int(x)
    return x.to_bytes(3, 'big')


def int32(x):
    x = int(x)
    return x.to_bytes(4, 'big')


def inet_aton(addr):
    dots = addr.count('.')
    if dots == 2:
        # a.b.c
        a_b, c = addr.rsplit('.', 1)
        a_b = socket.inet_pton(socket.AF_INET, a_b + '.0.0')
        return a_b[:2] + int16(c)
    elif dots == 1:
        # a.b
        a, b = addr.rsplit('.', 1)
        a = socket.inet_pton(socket.AF_INET, a + '.0.0.0')
        return a[:1] + int24(b)
    elif dots == 0:
        # a (32 bits)
        return int32(addr)
    else:
        # Expect a.b.c.d format
        return socket.inet_pton(socket.AF_INET, addr)

def test(addr):
    b = socket.inet_aton(addr)
    a = inet_aton(addr)
    assert a == b, (a, b)

test('127.0.0.1')
test('127.0.65535')
test('127.16777215')
test('4294967295')