list sort question

[Erik Max Francis]

Bill Tolbert wrote:

> I was asked today to sort a list of names and email addresses by last
> name. I ended up with a list of tuples:
> 
> [('Bill Tolbert', 'bill_tolbert at bigfoot.com'), ...]
> 
> I couldn't figure out the list.sort(somefunction) syntax and resorted
> to
> all sorts of slicing before I gave up and solved it in a query
> (outside
> of Python).

The function passed to sort takes two arguments, and must return -1, 0,
or 1 if the first is less than, equal to, or greater than the second
(respectively).

To get the last name of one of your tuples, you'd want something like

    import string

    tuple = ('Bill Tolbert', 'bill_tolbert at bigfoot.com')
    string.split(tuple[0])[-1] # take the first element, 
                               # split it into words, 
                               # take the last word

So to sort the list you could do something like:

    list.sort(lambda x, y: cmp(string.split(x[0])[-1],  
                               string.split(y[0])[-1]))

Now this would be pretty unwieldy on anything but tiny lists.  If you
are expecting to have even relatively sizeable lists, you'd probably
want to choose another data structure (another poster suggested a
dictionary whose keys are the last name and whose values are the
tuples).

-- 
 Erik Max Francis / max at alcyone.com / http://www.alcyone.com/max/
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