def seconds2walltime(seconds):
    """convert a time in seconds to [[HHH:[MM:]SS

    >>> seconds2walltime(12)
    '00:00:12'
    >>> seconds2walltime(123)
    '00:02:03'
    >>> seconds2walltime(1234)
    '00:20:34'
    >>> seconds2walltime(12345)
    '03:25:45'
    """
    seconds = int(seconds)
    secs = seconds % 60
    seconds = seconds // 60
    mins = seconds % 60
    hours = seconds // 60
    return '{h:02d}:{m:02d}:{s:02d}'.format(h=hours, m=mins, s=secs)
