Python：根据 dataframe 中的现有列添加带有日期的新列

Question

have a df with values:

   name        date
0   tom  01-07-2006
1   tom  07-07-2006
2   tom  13-07-2006
3   tom  19-07-2006
4  mark  01-07-2006
5  mark  07-07-2006
6  mark  13-07-2006
7  mark  19-07-2006

How to add a column min date which is minimum of date + 1

expected_output:

   name        date  min date
0   tom  01-07-2006  02-07-2006
1   tom  07-07-2006  02-07-2006
2   tom  13-07-2006  02-07-2006
3   tom  19-07-2006  02-07-2006
4  mark  02-07-2006  03-07-2006
5  mark  07-07-2006  03-07-2006
6  mark  13-07-2006  03-07-2006
7  mark  19-07-2006  03-07-2006

Answer 1

Convert column to datetimes, then get minimal per groups by GroupBy.transform and last add 1 day by Timedelta :

df['date'] = pd.to_datetime(df['date'], dayfirst=True)

df['min date'] = df.groupby('name')['date'].transform('min') + pd.Timedelta(1, 'd')
print (df)
   name       date   min date
0   tom 2006-07-01 2006-07-02
1   tom 2006-07-07 2006-07-02
2   tom 2006-07-13 2006-07-02
3   tom 2006-07-19 2006-07-02
4  mark 2006-07-02 2006-07-03
5  mark 2006-07-07 2006-07-03
6  mark 2006-07-13 2006-07-03
7  mark 2006-07-19 2006-07-03