Pandas groupby with delimiter join

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Pandas groupby with delimiter join

I tried to use groupby to group rows with multiple values.

col val
A  Cat
A  Tiger
B  Ball
B  Bat
import pandas as pd
df = pd.read_csv("Inputfile.txt", sep='t')
group = df.groupby(['col'])['val'].sum()

I got

A CatTiger
B BallBat

I want to introduce a delimiter, so that my output looks like

A Cat-Tiger
B Ball-Bat

I tried,

group = df.groupby(['col'])['val'].sum().apply(lambda x: '-'.join(x))

this yielded,

A C-a-t-T-i-g-e-r
B B-a-l-l-B-a-t

What is the issue here ?



Asked By: Arun


Answer #1:

Alternatively you can do it this way:

In [48]: df.groupby('col')['val'].agg('-'.join)
A    Cat-Tiger
B     Ball-Bat
Name: val, dtype: object

UPDATE: answering question from the comment:

In [2]: df
  col    val
0   A    Cat
1   A  Tiger
2   A  Panda
3   B   Ball
4   B    Bat
5   B  Mouse
6   B    Egg
In [3]: df.groupby('col')['val'].agg('-'.join)
A       Cat-Tiger-Panda
B    Ball-Bat-Mouse-Egg
Name: val, dtype: object

Last for convert index or MultiIndex to columns:

df1 = df.groupby('col')['val'].agg('-'.join).reset_index(name='new')
Answered By: MaxU

Answer #2:

just try

group = df.groupby(['col'])['val'].apply(lambda x: '-'.join(x))
Answered By: ??????
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