In Paris, public transport is available between 11 a.m. and 5 p.m., which is complicated when you are not retired.
With winter clothes, it's intolerable, you'd have to come in a tank top. When tourists arrive for the Olympics, they will be entitled to wonder if the passengers of the Paris metro might not, by chance, be great apes (without sphincters, therefore) The next day, another option: the bus. A brief glance at the seats dissuades you from sitting down unless you have Kevlar pants.