I agree the doc is far from perfect. The bit I was going off is just above <https://docs.python.org/3.5/library/socket.html#socket.socket.family>, saying “these (read-only) attributes that correspond to the values given to the socket constructor”.

My instinct would be to clarify that for existing versions 2.7, 3.5, etc, that the constructor arguments are _not_ ignored and should correspond to the file descriptor. Then in the next Python version we can make it more automatic using the getsockopt() techniques.