A simple and fast Python 3.6+ function for formatting an integer representing time in seconds to HH:MM:SS or d-HH:MM:SS format.

format_time.py

def formatTime(tS):
    """Format a time in seconds in HH:MM:SS format or d-HH:MM:SS format
    if a full day or longer.
    """
    if isinstance(tS, int):
        if tS >= 86400:
            return f"{tS//86400:d}-{tS%86400//3600:02d}:{tS%3600//60:02d}:{tS%60:02d}"
        else:
            return f"{tS//3600:02d}:{tS%3600//60:02d}:{tS%60:02d}"
    return "ERROR"