utils.py

import asyncio


async def async_zip_stream(*iterators, default_value=''):
    tasks = [asyncio.create_task(iterator.__anext__()) for iterator in iterators]
    done = [False] * len(iterators)

    while not all(done):
        results = []

        for i, task in enumerate(tasks):
            if done[i]:
                results.append(default_value)
            elif task.done():
                try:
                    results.append(task.result())
                    tasks[i] = asyncio.create_task(iterators[i].__anext__())
                except StopAsyncIteration:
                    done[i] = True
                    results.append(default_value)
            else:
                results.append(default_value)

        yield tuple(results)
        await asyncio.sleep(0.01)  # Slight delay to allow other tasks to progress