deque using array.py

class Error(Exception):
    pass


class Deque:
    def __repr__(self):
        arr = []
        for i in range(self.length):
            arr.append(self.popleft())
        for x in arr:
            self.append(x)
        return str(arr)

    def __init__(self, maxsize):
        self.length = 0
        self.maxsize = maxsize
        self.head = self.tail = 0
        self.arr = [None] * (self.maxsize)

    def appendleft(self, item):
        if self.full():
            raise Error('queue is full')
        self.arr[self.tail] = item
        self.length += 1
        self.tail = (self.tail + 1) % self.maxsize

    def pop(self):
        if self.empty():
            raise Error('queue is empty')
        result = self.arr[self.head]
        self.arr[self.head] = None
        self.length -= 1
        self.head = (self.head + 1) % self.maxsize
        return result

    def append(self, item):
        if self.full():
            raise Error('queue is full')
        self.head = (self.head - 1) % self.maxsize
        self.arr[self.head] = item
        self.length += 1

    def popleft(self):
        if self.empty():
            raise Error('queue is empty')
        self.tail = (self.tail - 1) % self.maxsize
        result = self.arr[self.tail]
        self.arr[self.tail] = None

        self.length -= 1
        return result

    def empty(self):
        return self.length == 0

    def full(self):
        return self.length == self.maxsize

    def front(self):
        if not self.empty():
            return self.arr[self.head]

    def end(self):
        if not self.empty():
            return self.arr[self.tail]


'''
q = Deque(4)
print(q)
q.appendleft(4)
print(q)
q.append(5)
print(q)
q.appendleft(3)
print(q)
print(q.pop())
print(q)
print(q.popleft())
print(q)
q.append(5)
print(q)
q.appendleft(2)
print(q)'''