Halloween is typically not celebrated by French people, though stores in France may sell pumpkins and encourage people to buy them for carving. Halloween enjoyed a bit more popularity in France several years ago, but has not anchored itself into French culture as a major holiday. Some children do go trick-or-treating and people who choose to participate in the holiday give out candy.
Here are some expressions used by francophone children on doorsteps instead of the English “trick or treat!” :
“La charité, s’il vous plaît” (Quebec, older expression)
“Des bonbons ou un sort!” (France)
“On veut des bonbons!” (France)