import socket


def is_ipv4_address(addr):
    """ 
    Check if an address is a valid IPv4 address
    Note that something like '1.1.1' is considered to be valid. 
    Because '1.1.1' can be abbreviation of '1.1.1.0'
    """
    try:
        socket.inet_aton(addr)
        return True
    except (socket.error, ValueError):
        return False