Painting my room

If I paint my room in emulsion/gloss paint, will 2 days be sufficient to keep my snake away if I keep the windows open to provide good ventilation.

One day should be plenty of time so long as there's decent ventilation.

Gloss will take longer to dry, so, your two day suggestion sounds about right, possibly three. The key will be whether or not you still smell paint when you walk into the room...

I waited a couple days after using a flat latex, which drys a lot quicker.