> In France who has the right of way? The car that is already in the roundabout or the car entering the roundabout?

Actually it's pretty consistent all across Europe. Almost everywhere, every entrance to the roundabout has the yield sign [1]. Without the yield sign, every incoming traffic is right hand traffic and those already on the roundabout have to give a way.

Now the trick is that yield signs at the entrance are so common that drivers assume they are always there.

[1] https://en.wikipedia.org/wiki/Yield_sign

> In France who has the right of way? The car that is already in the roundabout or the car entering the roundabout?

The answer is, it depends, pay attention to the signs! Most of the time it’s the car on the roundabout, but not always.

In France, in absence of contrary indications (ie: absence of signs, traffic signals, or line markings), it's "Priority to the Right".

So if it's an actual roundabout (aka, "rond-point"), then normal traffic rules apply for intersections: Priority to the Right. Vehicles already on the roundabout must yield to cars entering it.

Often, you have what is referred as "Carrefours à sens giratoire", which can very much look like "rond-points", but priority is to the vehicles already on the roundabout. For this reason, there will be a yield sign at the entrance of the roundabout to make it clear there's a special rule that applies to it. Sometimes you have traffic lights as well.