test_x_1 = test_x.copy()
for i, j in zip(test_x.columns.values, test_x.dtypes.values):
if j == 'object':
diff = list(set(test_x[i].unique()) - set(unique_df[i].unique()))
print i, len(diff)
if len(diff) > 0:
test_x_1.loc[(test_x[i].isin(diff)), i] = test_x[i].value_counts().idxmax()