getattr_sub.py

def getattr_sub(obj, attrs, default='__default__'):
    """ 
    >>> getattr_sub(int, '__class__.__name__', None)
    'type'
    >>> getattr_sub(int, '__cleese__.__name__', 'missing')
    'missing'
    """
    if type(attrs) == str:
        attrs = attrs.split('.')
        
    cur = obj
    for a in attrs:
        cur = getattr(cur, a, '__attr_error__')
        if cur == '__attr_error__':
            break
    
    if cur != '__attr_error__':
        return cur
    
    if default != '__default__':
        return default
    
    msg = "object does not have the subattattribute %s"
    raise AttributeError(msg % attrs.join('.'))