Metro Train Question

have you ever seen train tracks with switches? they don't turn the train around. It just stops at terminus and then starts back up going the opposite direction from which it came. The switches on the tracks will be maneuvered to put in onto the correct track.

Most trains are multi-directional. Driver just moves from one end of the train to the other and, voila, its is now the front of the train.
There are extensive repair yards where they can pick them up, turn them around, pretty much anything they want with them.

Same method as a terminal stations for non-métro trains (gare du Nord, gare de Lyon etc.), it just goes the other way.
The trains are totally symmetrical. That is why all the questions about "how do I book a seat going forwards" cannot always be answered, any seat that is going forwards from A to B, is going backwards from B to A, and vice-versa.

But, there are some line ends where the there is a loop of track and the train does a "U turn". This saves time as the driver does not have to change ends.
For the nerds amongst you, there is a track map of the whole of the Paris métro here: http://carto.metro.free.fr/cartes/metro-paris/
If you look at the western end of Line 2 (Blue, Porte Dauphine) you can see a loop. But most lines end, with crossover tracks so the train can go back on the opposite track in the opposite direction.

Chris F, thanks for posting about line 2. I had this vague memory of a metro line with a loop and line 2 popped into my head but I had no idea how to look that up.

Line 2 is a particularly weird example as the train turns through a loop at the official terminal, Porte Dauphine, but then reverses at the actual terminal, Victor Hugo. This means that if you get on a Nation-bound train at Porte Dauphine, you have to change trains across the platform at Victor Hugo, which isn't always announced.