def get_float(value):
    """
    Convert a string to a float number

    :param value: (str)
    :return: (float)

    Example:
    >>> get_float('3.0')
    3.0

    """
    try:
        ret = float(value)
    except ValueError:
        raise ValueError("Could not convert '%s' into a float number" % value)
    return ret