import trio
import gc


class RAII:
    def __del__(self):
        print('Goodbye.')


class InefficientReader:

    def __init__(self):
        self._remaining = b'1' * 256 * 1024 * 1024

    async def _iter_head(self):
        raii = RAII()

        head = self._remaining[:16]
        remaining = self._remaining[16:]
        self._remaining = remaining[:]
        yield head

        yield self._remaining

        assert raii

    async def get_head(self):
        async for chunk in self._iter_head():
            return chunk


async def iterate():
    reader = InefficientReader()

    for i in range(20):
        print(i)

        chunk = await reader.get_head()
        if not chunk:
            break

        gc.collect()


def test():
    trio.run(iterate)