def progress(iterator, prefix):
    """Progress an iterator and updates a pretty status line to the terminal.

    The status line contains:
     - Amount of data read from the iterator
     - Time elapsed
     - Average speed, based on the last few seconds.
    """
    prefix = (".." + prefix[-23:]) if len(prefix) > 25 else prefix
    speed_updated = start = time()
    speed_written = written = 0
    speed_history = deque(maxlen=5)

    for data in iterator:
        yield data

        now = time()
        elapsed = now - start
        written += len(data)

        speed_elapsed = now - speed_updated
        if speed_elapsed >= 0.5:
            speed_history.appendleft((
                written - speed_written,
                speed_updated,
            ))
            speed_updated = now
            speed_written = written

            speed_history_written = sum(h[0] for h in speed_history)
            speed_history_elapsed = now - speed_history[-1][1]
            speed = speed_history_written / speed_history_elapsed

            status = create_status_line(
                prefix=prefix,
                written=format_filesize(written),
                elapsed=format_time(elapsed),
                speed=format_filesize(speed)
            )
            print_inplace(status)
Progress an iterator and updates a pretty status line to the terminal.

    The status line contains:
     - Amount of data read from the iterator
     - Time elapsed
     - Average speed, based on the last few seconds.
    
src/livestreamer_cli/utils/progress.py