There are several options for purchasing bus tickets for the ATAF Florence city buses, my favorite was always the 10 trip carnet normally available at the larger tabacchi, or coffee bars. Once you are in Florence, you will find that the bus is great for getting to the longer distances (like the train station to Piaza Michelangelo) - but Florence is so compact that the shorter distances are easier to do by foot (and so much more exciting!)
The Carnet doesn't need to be physically stamped (read this article for some warnings https://www.visitflorence.com/moving-around-florence/by-bus.html) but you do need to tap it up to the green box visible at the front of the bus when you enter so that the ticket is activated AND you must do this for each and every trip! If you catch two buses in a row (within the time frame permited for a ticket - 90 min) you won't need to re-tap the ticket, it will keep track for you. BUT if you do re-tap it, no worries, it will not activate another one of your 10 trips, it knows how to keep time.
There is a full day ticket option, however, it is tied to having a Pegaso card, which requires a registration process that doesn't appear to be worth the trouble for 7 days.
You will find the latest information for bus tickets here at the ATAF official website:
More simply put: no, there is no longer a 7 day pass offered that is easily used by visitors to the city.
Local transport has changed options to make people get monthly and yearly passes, getting rid of lots of the shorter passes. Even the carnets that Donna has mentioned above are not easy to find anymore (they do exist but not all places have them), nor the 4 tickets in one ticket that used to be sold before. You'll have to buy single tickets at bars/tabacchi shops if you can't find the carnet and use as you go.