[Tutor] high score lists

[Max Noel]

On Apr 15, 2005, at 01:33, D. Hartley wrote:

> This is what I have so far:
>
> high_scorelist = [(1000,"Denise"), (945,"Denise"), (883,"Denise"),
>                  (823,"Grant"), (779,"Aaron"), (702,"Pete"),
>                  (555,"Tom"), (443,"Tom"), (442,"Robin"), (404,"Pete")]
>
> userscore = (441,"Joe")
>
> def add_score(userscore):
>    if userscore[0] > high_scorelist[len(high_scorelist)-1][0]:
>        print "You made the high score list!"
>        high_scorelist.append(userscore)
>        high_scorelist.sort(reverse=True)
>        del high_scorelist[len(high_scorelist)-1]
>        return high_scorelist
>    else:
>        print high_scorelist

	Okay, a few little comments:
- high_scorelist[len(high_scorelist)-1] can be written as 
high_scorelist[-1]. Python slicing operators are very powerful.
- That's me nitpicking, but you should pick a naming convention for 
your whole program (camelCase, names_with_underscores or whatever) and 
stick to it. It makes things more readable. For example, userscore and 
high_scorelist should be named userScore and highScoreList, or 
user_score and high_score_list.
- Since lists are mutable objects, the function add_score, by way of 
the append and sort methods, modifies the high_scorelist list in place. 
Why do you return it afterwards?

> I had to enter in the variable for "userscore" like that, when I add a
> tuple directly into the add_score function, it seems to delete the
> last item in the list (i.e., the one I just added) BEFORE it sorts it
> (i.e., removing the lowest score).  I have no idea why this is.  But
> if I define userscore = (465,"Jane"), for instance, and then run
> add_score(userscore), it'll change and print my 10-person high score
> list, just like I want it to.

	What did your code look like when it did that?

> (I also
> just ended up writing the list like [score,user] because I couldnt
> figure out how to get it to sort by the second half of the tuple.  I
> need a better tutorial book, I think!)

	Not really. Writing things that way is the natural thing to do (even 
though it might feel counter-intuitive at the beginning), as it allows 
you to do what you want without extra code, and the less code you write 
for a given functionality, the better. Every line of code you write is 
a liability.
	Formatting data for display is left to the programmer (i.e. you). The 
user never sees what the internal data structure looks like, so when 
you're designing it, the only thing you should take into account is how 
easy to use it's going to be for *you*, the programmer.

> but they don't always explain
>  everything (such as what the "cmp=None, key=None" means in the ( )
>  helper of the .sort function.  I figured reverse=True/False out by
>  playing with it).

	cmp is a user-supplied comparison function. When it is given 2 
arguments, x and y, it must return -1 when x < y, 0 when x == y and 1 
when x > y. it allows you to sort the list based on arbitrary criteria 
without having to re-write a sort function.
	If it is None, the default sort function is used.
	I'm still using Python 2.3, so someone else will have to tell you what 
the "key" argument is.

	Oh, and when you're wondering what something does, remember that:
- Experimenting is good.
- Your 2 best friends are the interactive Python shell, and the help() 
function.

-- Max
maxnoel_fr at yahoo dot fr -- ICQ #85274019
"Look at you hacker... A pathetic creature of meat and bone, panting 
and sweating as you run through my corridors... How can you challenge a 
perfect, immortal machine?"