When "except" means the same as "but", you can use either "except" or "except for".

Everybody is asleep except for Mary. OR Everybody is asleep except Mary. OR Everybody is asleep but Mary.

BUT

The bus was empty except for me. does NOT mean the same as
The bus was empty but me.

There was nobody on the bus but me. OR There was nobody on the bus except for me. OR There was nobody on the bus except me.

Does this help you, Mike?