[pandas] [tutorial] find missing columns

ix_row, ix_col = np.where(np.asanyarray(np.isnan(df)))
prods = pd.DataFrame({'row_idx':ix_row,
                      'col_idx':ix_col})
b = [-np.inf] + np.arange(len(df.columns)).tolist() + [np.inf]
l = ['Error'] + df.columns.tolist()
prods['label'] = pd.cut(prods['col_idx'], bins=b, labels=l, right=False)
prods = prods.drop(['col_idx'], axis=1)