def readable_duration(seconds: float, pad: str = "") -> str:
    """Produce human-readable duration."""
    if seconds < 10:
        return f"{seconds:.2g}s"
    seconds = int(round(seconds))

    parts = []

    time_minute = 60
    time_hour = 3600
    time_day = 86400
    time_week = 604800

    weeks, seconds = divmod(seconds, time_week)
    days, seconds = divmod(seconds, time_day)
    hours, seconds = divmod(seconds, time_hour)
    minutes, seconds = divmod(seconds, time_minute)

    if weeks:
        parts.append(f"{weeks}w")
    if days:
        parts.append(f"{days}d")
    if hours:
        parts.append(f"{hours}h")
    if minutes and not weeks and not days:
        parts.append(f"{minutes}m")
    if seconds and not weeks and not days and not hours:
        parts.append(f"{seconds}s")

    return pad.join(parts)