def is_numeric(s):
    """
    Return True is the string ``s`` is a numeric string.

    Parameters
    ----------
    s : str
        A string.

    Returns
    -------
    res : bool
        If True, ``s`` is a numeric string and can be converted to an int or a
        float. Otherwise False will be returned.

    """
    try:
        float(s)
    except ValueError:
        return False
    else:
        return True