columnpairs = [(i, j) for i in new.columns[1:] for j in master.columns[1:] if
    i != j]
summary_dict = {col: [] for col in new.columns[1:]}
for p in columnpairs:
    i, j = p
is_same = (new['Characteristic'] == master['Characteristic']) & (new[i] ==
    master[j]) & (new[i] != '--') & (master[j] != '--')
pct_same = sum(is_same) * 100 / len(master)
if pct_same > 90:
    summary_dict[i].append({'match': j, 'pct': pct_same})
print(summary_dict)
Pandas: Compare a column to all other columns of a dataframe