How to fix python program that appears to be doing an extra loop?

A portion of a python program I am writing seems to be looping an extra time. The part of the program that isn't working is below. It is supposed to ask for a string from the user and create a two-dimensional list where each distinct character of the string is put in its own sub-list. (Hopefully that makes sense... if not I can try to explain better. Perhaps the code will help)

def getInput(emptyList):
    inputString = input("Please enter a sentence:\n").strip().upper()
    functionList = [x for x in inputString]
    emptyList.extend(functionList)
    return 0

def sortList(listA,listB):
    listA.sort()
    currentElement = listA[0]
    compareTo = listA[0]
    elementsCounted = 0
    i = 0
    listB.append([])
    while elementsCounted  < len(listA):
        while currentElement == compareTo:
            listB[i].append(currentElement)
            elementsCounted += 1
            print(listB)
            if elementsCounted < len(listA):
                currentElement = listA[elementsCounted]
            else:
                break
        if currentElement != compareTo:
            i += 1
            listB.append([])
            compareTo = listA[i]

    return 0

def main():
    myList = list()
    sortedList = list()
    getInput(myList)
    sortList(myList,sortedList)
    print(sortedList)

main()

If the user enters qwerty, the program returns [['E'], ['Q'], ['R'], ['T'], ['W'], ['Y']] which is correct but if the user enters qwwerrty the program returns [['E'], ['Q'], ['R', 'R'], [], ['T'], ['W', 'W'], [], ['Y']]. Note the extra empty list after each "double" character. It appears that the loop is making one extra iteration or that the if statement before listB.append([]) isn't written properly.

I can't seem to figure it out more than this. Thank you in advance for your help.