In 2018 two new crimes will be added to the Swedish penal code: "negligent rape" and "negligent sexual assault". These will make it illegal to have sex without obtaining active consent. A person must agree in words or clear actions to sex, otherwise it will be considered rape. It's not in effect yet, but widely supported and will be in effect in July 2018.
Of course this whole law is pointless, since verbal consent cannot be proven. A woman in Sweden can nevertheless file rape against you without having to provide any evidence. The case will be dropped at some point, but a drawn out process will ruin you socially either way. We can be sure that this law will never be used against certain gentlemen who clearly don't upset this liberal community.
So in Sweden you now need written consent, just to make sure you're safe and her vagina is completely dry, and you cannot even get sex elsewhere