[Tutor] high score lists

[Jacob S.]

> You can think of the "key" option like this: when sort comes to compare 
> elements x and y it gives you the option of telling *what* you want to 
> compare about x and y.  You might, for example, want to sort a list of 
> strings based on their *length* not on their alphabetical position. To do 
> so, write a 1-argument function that returns the length of a string:
>
> ###
> Python 2.4 (#1, Apr  4 2005, 13:57:19)
> [GCC 3.3 20030304 (Apple Computer, Inc. build 1493)] on darwin
> Type "help", "copyright", "credits" or "license" for more information.
> >>> l=['sea', 'd', 'bee']
> >>> l.sort()              #the normal sort
> >>> l
> ['bee', 'd', 'sea']
> >>> def strlen(x):        # the 1-argument function
> ...     return len(x)
> ...
> >>> l.sort(key=strlen)
> >>> l
> ['d', 'sea', 'bee']      #the length sort; it's stable so sea is still 
> before bee
> >>> def length_alph(x):  #'key' function if you want length first and
> then alphabetical
> ...     return (len(x),x)
> ...
> >>> l.sort(key=length_alph); l
> ['d', 'bee', 'sea']
> ###

Great.  len is a function though. Why use a second layer of function when 
len is a function in itself?

>>> l = ['d','sea','bee']
>>> l.sort(key=len)
>>> l
['d', 'bee', 'sea']
>>>

Jacob