newbie/ merging lists of lists with items in common

[ardief]

Hi everyone
Here is my problem:
I have a list that looks like this -
[['a', '13'], ['a', '3'], ['b', '6'], ['c', '12'], ['c', '15'], ['c',
'4'], ['d', '2'], ['e', '11'], ['e', '5'], ['e', '16'], ['e', '7']]

and I would like to end up with something like this, i.e. with the
only one list per letter:

[['a', ['13' '3']], ['b', '6'], ['c', ['12', '15', '4']], ['d', '2'],
['e', ['11', '5', '16', '7']]]

I have the feeling it's trivial, and I've scoured the group archives -
sets might be a possibility, but I'm not sure how to operate on a list
of lists with sets.

This function also gives me what I want, more or less, but I don't
know how to make it run until it's covered all the possibilities, if
that makes sense...

def sigh(list):
	for a in list:
		i = list.index(a)
		if a != list[-1]:    ##if a is not the last one, i.e. there is a
next one
			n = alist[i+1]
			if a[0] == n[0]:
				a.append(n[1:])
				del alist[i+1]

Sorry about the lengthy message and thanks for your suggestions - I'm
trying to learn...