Python deque implementation

class deque:
    def __init__(self):
        self._data = []

    def add_front(self, i):
        self._data.insert(0, i)

    def add_back(self, i):
        self._data.append(i)

    def remove_front(self):
        return self._data.pop(0)

    def remove_back(self):
        return self._data.pop()

    def front(self):
        return self._data[0]

    def back(self):
        return self._data[-1]

    def is_empty(self):
        return len(self._data) == 0

    def __str__(self):
        return self._data.__str__()