The name can be any str/unicode string, including language keywords: 

    >>> setattr(o, 'def', 'allowed')
    >>> getattr(o, 'def')
    'allowed'
    >>> o.def
      File "<stdin>", line 1
        o.def
            ^
    SyntaxError: invalid syntax

and even an empty string:

    >>> setattr(o, '', 'mu')
    >>> getattr(o, '')
    'mu'

This includes instances of str and unicode subclasses, at least in CPython.