select nan value

[scidam]

Take a look at the following example:

import pandas as pd
df = pd.DataFrame({"A": [1, pd.np.nan], "B": [pd.np.nan, 2]})
df.loc[df.A.isna(), "C"] = df.B[df.A.isna()]
df.loc[df.B.isna(), "C"] = df.A[df.B.isna()]