I've been hit by this too, in similar contexts, and several times. It is really annoying that it is easier to coerce an UUID or UUID-string to a string than to coerce to a UUID. Usually when the copy semantics are clear and the class is plain old data, Python lets you execute the constructor with an instance of the same class:

    >>> bytes(bytes())
    b''
    >>> bytearray(bytearray())
    bytearray(b'')
    >>> int(int())
    0
    >>> complex(complex())
    0j
    >>> tuple(tuple())
    ()

I don't to see why this shouldn't be true with UUID as well.