def datetime_to_pretty_str(dt):
    """
    Convert datetime object to string similar to ISO 8601 but more compact.

    Arguments:
    ----------
    dt: dateime object
        ... for which the string will be generated.

    Returns:
    --------
    dt_str: string
        The pretty string respresentation of the datetime object.
    """
    dt_str = dt.strftime('%Y-%m-%d %H:%M:%S')
    return dt_str