def seconds2string(number):
    """
    Convert time in seconds to 'HH:MM:SS' format

    Parameters
    -----------
    number : float
        value in seconds

    Returns
    -------
    time_string : str
        time in 'HH:MM:SS' format

    Example
    -------
    >>> from ISPy.io import solarnet
    >>> solarnet.seconds2string(63729.3)
    '17:42:09.300000'

    :Author:
        Carlos Diaz Baso (ISP/SU 2019)
    """
    hour = number//3600.
    minute = (number%3600.)//60.
    seconds = (number-(hour*3600.+minute*60))/1.
    string_output = '{0:02}:{1:02}:{2:09.6f}'.format(int(hour),int(minute),seconds)
    return string_output