for combo in col_combos:
    match_count = np.count_nonzero(new_master[combo[0]] == new_master[combo[1]]
        )
pct_same = match_count * 100 / len(new_master)
if pct_same > 90:
    summary_dict[combo[0]].append({'match': combo[1], 'pct': match_count /
        len(new_master)})
print(summary_dict)
{'S4': [], 'S5': [{'pct': 1.0, 'match': 'S2'}]}
Pandas: Compare a column to all other columns of a dataframe