ring.py

from collections import deque


class RingBuff:
    """
    # Spec for buffer
    >>> buffer = RingBuff(5)
    >>> buffer.write([1, 2, 3])
    3
    >>> buffer.write([4, 5, 6])
    2
    >>> buffer.read()
    1
    >>> buffer.read()
    2
    >>> buffer.read()
    3
    >>> buffer.read()
    4
    >>> buffer.read()
    5
    >>> buffer.read()
    Traceback (most recent call last):
    ...
    IndexError: Empty ring
    """

    def __init__(self, capacity=5):
        self.fifo = deque(maxlen=capacity)
        self.capacity = capacity

    def write(self, objects: [object]) -> int:
        size = self.capacity - len(self.fifo)
        size = min(len(objects), size)
        for o in objects[:size]:
            self.fifo.append(o)
        return size

    def read(self) -> object or IndexError:
        try:
            return self.fifo.popleft()
        except IndexError:
            raise IndexError("Empty ring")

    def __repr__(self) -> str:
        return f"RingBuff<{self.fifo}>"


def main():
    import doctest

    doctest.testmod()


if __name__ == "__main__":
    main()