def df_row_to_com_dict(df_row):
    """ From a single row of df, return comp dict
        key: isotope (e.g. pu-239)
        value: % mass
    """

    iso_list = list(df_row)[5:]
    assem_dict = df_row.to_dict()
    assem_dict = {key: assem_dict[key] for key in assem_dict if key in iso_list}
    return assem_dict