def is_ipv4(s):
    """ Tests if `s` is a IPv4 address string.
		It only validates the common `x.x.x.x` format and rejects less common ones like `x.x`.
	"""
    try:
        nums = tuple(map(int, s.split('.')))
        return len(nums) == 4 and min(nums) >= 0 and max(nums) <= 255
    except (AttributeError, ValueError):
        return False
