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Pandas: Group by the first column and get second column as lists in rows

Pandas: DataFrame Exercise-55 with Solution

Write a Pandas program to group by the first column and get second column as lists in rows.

Sample Solution :

Python Code :

import pandas as pd
df = pd.DataFrame( {'col1':['C1','C1','C2','C2','C2','C3','C2'], 'col2':[1,2,3,3,4,6,5]})
print("Original DataFrame")
print(df)
df = df.groupby('col1')['col2'].apply(list)
print("\nGroup on the col1:")
print(df)

Sample Output:

Original DataFrame
  col1  col2
0   C1     1
1   C1     2
2   C2     3
3   C2     3
4   C2     4
5   C3     6
6   C2     5

Group on the col1:
col1
C1          [1, 2]
C2    [3, 3, 4, 5]
C3             [6]
Name: col2, dtype: object       

Python-Pandas Code Editor:

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>>> words = ('Hello', 'Python', 'Programmers')
>>> '!'.join(words)
'Hello!Python!Programmers'
>>> words_dict = {0: 'zero', 1: 'one', 2: 'two', 3: 'three'}
>>> '&'.join(words_dict.values())
'zero&one&two&three'