Calculating a game's high score table

I need to create a function/method ( in python) which calculates开发者_JAVA技巧 a high score "leaderboard". Each player will have played any number of rounds of the game, recieving a score for each round. I want to know what's the best way to sort the top ranking players (accounting for score AND number of rounds played). The possible scores for each round are F, D-, D, D+, C-, C, C+, B-, B, B+, A-, and A.

Obviously a simple average won't work because it doesn't take into account number of rounds played. Whats the best way to set up a fair sorting function?

EDIT: I've been reading some of the really great answers here and I want to try to clear up my question a bit. I want both the players score AND the number of rounds they've played to count towards their ranking in a way that's fair. Meaning a player with 20 B's should be of a higher rank than a player with 5 A's. Basically the high score should reflect general effort and skill, "the number of rounds played PLUS their score" means the higher their ranking should be.

EDIT 2: After reading the answers, I think the best way to do it is a simple total sum of the players points across all rounds. I'm not sure which answer to assign the green check to because you were all correct.

There are many ways that you could do this. Try this for example, let F-A be 0-11 (you can make your own; however try to take difficulty into account), so each score is one higher than the previous. For every game you play, you receive a score (from 0-11). Create a total score and add the game score every time to the total score. That way, if a person receives 7 A's, that's 77, while a person that receives 7 A-'s gets a score of 70, then simply sort them accordingly. Each function has its drawbacks of course. This function is not the "best", consider getting 20 B's would exceed 7 A's even though, 7 A's is a much better score. if you can give me more details about how you want to rank them, then it will be much easier to get the algorithm down.

What you are asking is essentially how we define "good" players and it's not an easy problem. As you mentioned, a simple average score or picking-the-highest-score will not be an ideal answer depending on your game design.

I'd like to recommend that you read about ELO rating system for Chess and other modified versions of it before you design your own player rating system.

One simple and possible way is you can set a window (like 10 most recent games) and use average score from the window. Players who play less games than this window would be "in placement" state. Again, it's not an easy problem and heavily depends on what your game is. Good Luck!

[UPDATE]

I assumed that your game is player vs. player. If not, this is another story. Most games just keep the highest score no matter how many times you play the game and that's going to be your entry in the leaderboard. Since you don't say anything about your game, I have no idea why it wouldn't be fair. As I mentioned earlier, you could set a window for avg. score or the highest score. You can even reset your leaderboard every month or remove players who haven't played for a week. It all depends on your game and what you want. Please remember that no matter what you do, make it sure that the rules are crystal clear for players otherwise they would be easily upset and frustrated.