def eV(E):
    """
    Returns photon energy in eV if specified in eV or KeV. Assumes that any
    value that is less than 100 is in KeV.

    Parameters
    ----------
    E : float
        The input energy to convert to eV

    Returns
    -------
    E : float
        Energy converted to eV from KeV    
    """
    if E < 100:
        E *= 1000.0
    return float(E)