Travel in Prague

You might be able to buy it in advance, but why bother?
Plus Prague is small and you will probably find yourself walking most places.

Larry, here's the link for Prague's public transport website (this is the link showing their fares, including their multi-day passes)
http://www.dpp.cz/en/fares-in-prague/

Larry There are three and five day passes which are good deals. You can purchase both at a transport kiosk which is directly opposite where you come out of customs, and at ticket offices at the major metro stations. The advantage of the former is that you can then use them to travel into the centre. Cheers Alan

I bought mine at the TI in the train station when I arrived from Vienna. The kind woman sold me several single day passes because, as she explained, they were cheaper than the multi-day pass. Whether to buy the pass depends on where you are staying. If you are lodging in the center, it probably doesn't pay. If you are staying farther out, it could be a good deal - allowing you to go back and forth (for a rest, a change of clothes, whatever) - and it's more convenient than individual tickets.

I am just a month back (sob) from Prague and I agree with the earlier message that you don't really need a pass if you're staying in the city center. All the major sites are within walking distance and the streets themselves are lively and fun.