Move The Value In The Second Duplicate To The First Duplicate

This post is to assign value of last row to first row: Move last value to first value. I would like to move the value in the second duplicate to the first duplicate and set others

Solution 1:

Let us do reindex with apply and select the second of row , then do the same as we did from pervious question

df['New']=df.groupby('DateOutBed')['OutBedTime'].apply(lambda x : x.iloc[[1]]).reset_index(level=1,drop=True).reindex(df.DateOutBed).values
df['New']=df.New.mask(df.DateOutBed.duplicated())
df
   ID      OutBedTime  DateOutBed             New
0116/05/20180:1716/05/201816/05/20184:051116/05/20184:0516/05/2018             NaN
2116/05/20186:0516/05/2018             NaN
3117/05/20181:2717/05/201817/05/20184:414117/05/20184:4117/05/2018             NaN
5117/05/20185:3217/05/2018             NaN

Check the update

df['New']=df.groupby('DateOutBed')['OutBedTime'].transform(lambda x : x.iloc[1] if len(x)>1 else x.iloc[0])
df['New']=df.New.mask(df.DateOutBed.duplicated())