Queue - implementacija

class Queue:
    def __init__(self):
        self._red  = [None]
        self._size = 0
        self._head = 0

    def sizeOf(self):
        return self._size

    def isEmpty(self):
        if (self._size == 0):
            return True
        return False

    def front(self):
        return self._red[self._head]

    def enQueue(self, element):
        # print self._red[(self._head + self._size)%len(self._red)]
        if self._red[(self._head + self._size)%len(self._red)] != None:
            self.expandQueue()

        self._red[(self._head + self._size)%len(self._red)] = element
        self._size += 1

    def deQueue(self):
        value = self._red[self._head]
        self._red[self._head] = None
        self._head = (self._head + 1)%len(self._red)
        self._size -= 1
        return value

    def expandQueue(self):
        lista = len(self._red)*2*[None]
        for i in range(len(self._red)):
            lista[i] = self._red[self._head]
            self._head = (self._head + 1) % len(self._red)

        self._red = lista
        self._head = 0

    def printQueue(self):
        for i in self._red:
            print str(i) + " ",
        print

red = Queue()

input()