def get_data_index(content, delimiter=None):
    """ Retrieve the index of the line where the data starts
    :param list of str content: list of strings
    :param str or None delimiter: delimiter of the float data

    Example
    -------
    >>> get_data_index(['first line', 'second line', '1 2 3'])
    2"""

    for index, line in enumerate(content):

        if line != '':
            try:
                [float(f) for f in line.split(delimiter)]
                return index
            except ValueError:
                continue