How to transfer values from one column to another column

Here is the DataFrame when I am doing Python using pandas.

import pandas as pd
import numpy as np
items = ['Apple','Cherry','Banana','Apple','Banana']
place = ['UK','','China','USA','China']
quality = ['Bad','Bad','Good','Bad','Good']
date = ['Jan-1','Jan-2','Jan-3','','Jan-1']

df = pd.DataFrame({"Item":items, "Place":place, "Quality":quality, "Date":date})
print(df)

What I require is:

• If column Placeis null and column Date is not null, then transfer the value from Date to Place;
• If column Placeis not null and column Date is null, then no transferring happens;
• If column Placeis and column Date is are both null or not null, then no transferring happens, either.

So I tried:

df.Place=np.where(df.Date!="",df.Date,df.Place)

but this can not be satisfied with what I require. The output should be like this:

Can someone help me with this solution? Thanks

>Solution :

The conditions of np.where seems to be incomplete:

df = df.replace('',np.nan)
df['Place'] = np.where(df['Place'].isna() & df['Date'].notna(), df['Date'], df['Place'])

or without replacing '' with NaN, just write the complete condition:

df.Place = np.where((df.Date!="") & (df.Place==""), df.Date, df.Place)

Output:

     Item  Place Quality   Date
0   Apple     UK     Bad  Jan-1
1  Cherry  Jan-2     Bad  Jan-2
2  Banana  China    Good  Jan-3
3   Apple    USA     Bad    NaN
4  Banana  China    Good  Jan-1