shuffle_queue.py

#!/usr/bin/env python3
import random as _rng


class ShuffleQueue:
    def __init__(self, items, rng=None):
        self._idx = 0
        self._items = items
        self._rng = rng or _rng

    def dequeue(self):
        upper = len(self._items)
        if self._idx == upper:
            return None

        swap = self._rng.randrange(self._idx, upper)
        self._items[self._idx], self._items[swap] = self._items[swap], self._items[self._idx]
        self._idx += 1
        return self._items[self._idx-1]

    def __next__(self):
        if (item := self.dequeue()) is None:
            raise StopIteration
        return item

    def __iter__(self):
        return self

    def requeue(self, item):
        if self._idx == 0 or item != self._items[self._idx-1]:
            return False

        self._idx -= 1
        return True

    def peek(self):
        return self._items[self._idx]


if __name__ == "__main__":
    for n in ShuffleQueue([1, 2, 3, 4, 5]):
        print(n)