Concatenating strings after grouping by name and then sorting by date

Question

I have this data in a data frame

data = [
           {'name' : 'a', 'date' : '2020-01-02', 'message' : 'there'},
           {'name' : 'b', 'date' : '2020-01-01', 'message' : 'Hello'},
           {'name' : 'a', 'date' : '2020-01-01', 'message' : 'Hi'},
           {'name' : 'b', 'date' : '2020-01-03', 'message' : 'everyone'},
           {'name' : 'c', 'date' : '2020-01-05', 'message' : 'Test'}
       ]

What I would like to do is group by name, then sort by date, and concatenate the message for each name so that the data looks like this

[
   {'name' : 'a', 'message' : 'Hi there'},
   {'name' : 'b', 'message' : 'Hello everyone'},
   {'name' : 'c', 'message' : 'Test'}
]

I have already been able to group by name and sort by date (after making the string into a datetime object) using this

df.groupby(['name']).apply(lambda x: x.sort_values(['date'])

but I am not sure how you would concatenate the strings together once you have grouped and sorted the data.

Answer 1

Try apply with join

df.sort_values('date').groupby('name')['message'].apply(' '.join).reset_index()

  name         message
0    a        Hi there
1    b  Hello everyone
2    c            Test