[Tutor] Problem with tuple and dictionary

[Mike Yuen]

I'm writing a larger program and for some reason, I keep getting an error
at the following:

matrix[(curr,last)] = int(diff)

Here's some more code in case the above line isn't the actual problem:
def compare (self, last, dict):
	#
	# Some other irrelevant stuff here
	#

	while (curr < last):
                        dcurr = dict[curr]
                        end = len(dict[last])

                        for index1 in range(end):
                                if dcurr[index1] != dlast[index1]:
                                        diff = diff + 1
                        matrix[(curr,last)] = int(diff) #WhAT's UP HERe?
                        curr = curr + 1 #Get next applicable dict entry
                        diff = 0
                        index1 = 0

Thanks,
M