Advertisements I have import pandas as pd import numpy as np df = pd.DataFrame({"x": ["red", "blue", np.nan, np.nan, np.nan, np.nan, np.nan, ], "y": [np.nan, np.nan, np.nan, ‘cold’, ‘warm’, np.nan, np.nan, ], "z": [np.nan, np.nan, np.nan, np.nan, np.nan, ‘charm’, ‘strange’], }).astype("category") giving x y z 0 red NaN NaN 1 blue NaN NaN 2 NaN NaN… Read More Combine multiple categorical columns into one, when each row has only one non-NaN value, in Pandas