ring_buffer.py

class RingBuffer:
    def __init__(self, capacity):
        self.capacity = capacity
        self.storage = []
        self.oldest_index = 0


    def append(self, item):
        if len(self.storage) < self.capacity:
            self.storage.append(item)
        else:
            self.storage[self.oldest_index] = item
            if self.oldest_index < len(self.storage) - 1:
                self.oldest_index += 1
            else:
                self.oldest_index = 0

    def get(self):
        return self.storage


# buffer = RingBuffer(3)

# buffer.get()   # should return []

# buffer.append('a')
# buffer.append('b')
# buffer.append('c')

# buffer.get()   # should return ['a', 'b', 'c']

# # 'd' overwrites the oldest value in the ring buffer, which is 'a'
# buffer.append('d')

# buffer.get()   # should return ['d', 'b', 'c']

# buffer.append('e')
# buffer.append('f')

# buffer.get()   # should return ['d', 'e', 'f']