Concatenate strings from several rows using Pandas groupby

Question

I want to merge several strings in a dataframe based on a groupedby in Pandas.

This is my code so far:

import pandas as pd

from io import StringIO

data = StringIO("""

"name1","hej","2014-11-01"

"name1","du","2014-11-02"

"name1","aj","2014-12-01"

"name1","oj","2014-12-02"

"name2","fin","2014-11-01"

"name2","katt","2014-11-02"

"name2","mycket","2014-12-01"

"name2","lite","2014-12-01"

""")

# load string as stream into dataframe

df = pd.read_csv(data,header=0, names=["name","text","date"],parse_dates=[2])

# add a column with the month

df["month"] = df["date"].apply(lambda x: x.month)

I want the end result to look like this:

I don't get how I can use groupby and apply some sort of concatenation of the strings in the column "text". Any help appreciated!

Answer 1

You can just call apply function and then reset_index, refer the following code:

In[38]:

df.groupby(['name','month'])['text'].apply(','.join).reset_index()

Out[38]: 

    name  month         text

0  name1     11   du

1  name1     12 aj,oj

2  name2     11 fin,katt

3  name2     12 mycket,lite

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