I get this question a lot. Let me try to address it, once and for all, here.
You can buy vegan foods except for vegan cold cuts, vegan cheese, non-dairy coffee creamer, non-dairy sour cream, and non-dairy whipped cream, in the average grocery store.
There are health food stores with better options out there. My favorite is BioCoop. (See my post about this.) They have vegan hot dogs, sliced cold cuts, spreadable cheeses and such.
The French, as a culture, have not heard of veganism (vegetalien), and will think you nuts. They will be 100 percent certain you are about to drop dead of this nightmare diet of yours, and will argue with you non-stop until they've saved you. It is better to say that you are a vegetarian (vegetarien). Then add that you are allergic to eggs and dairy.
I would 'piq-nic' for most of your meals to make sure you are eatting vegan. You can get gorgeous produce here, and some ready made foods, like hummas, packaged preped quinoa, olives, and, of course, bread, easily enough. Some of my favorite vegan packaged foods are listed on my blog as well.
In restaurants, bakeries, etc., good choices include...
Pain (French bread)
Salade verte (green salad)
Salade de fruits (fruit salad)
Pomme au four (baked potato)
I'll work on expanding this list as I think of things.
Word to love:
Lait soja (soy milk)
Lait almond (almond milk)
Lait avoine (oat milk)
Levure nutritionnelle (nutritional yeast)
100% Vegetal (a label you will see on products showing that they have no animal products in them
Words to avoid:
Feel free to copy this down and carry it with you to show people in restaurants. It may result in a vegan meal, though I offer you no guarantees. There is also the small chance you will be asked to leave by an unhappy chef. It says, "I am a vegetarian. I am also allergic to dairy products, including milk, butter, cream, cheese, and eggs. Would you please recommend a meal for me? Thank you!"
Je suis végétarien. Je suis également allergique aux produits laitiers, comme le lait, le beurre, la crème , le fromage et les œufs. Souhaitez-vous recommander un repas pour moi, s'il vous plaît ? Je vous remercie!
I hope that this helps. And I really hope you love my adoptive country! Bon appétit!