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
0   1  16/05/20180:17  16/05/2018  16/05/20184:05
1   1  16/05/20184:05  16/05/2018             NaN
2   1  16/05/20186:05  16/05/2018             NaN
3   1  17/05/20181:27  17/05/2018  17/05/20184:41
4   1  17/05/20184:41  17/05/2018             NaN
5   1  17/05/20185:32  17/05/2018             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())