def getattrs(obj, *attrs):
    """
    Get existing attributes of an object lazy

    >>> from argparse import Namespace
    >>> d = Namespace(henk=1, klaas=2, hent=7)
    >>> r = getattrs(d, "klaas")
    >>> list(r)
    [2]
    >>> r = getattrs(d, "henk", "hent")
    >>> list(r)
    [1, 7]
    >>> r = getattrs(d, "henk", "kak")
    >>> list(r)
    [1, None]
    """
    for attr in attrs:
        yield getattr(obj, attr, None)
