How do I roll up values to create a list in the cells of a dataframe per id using pandas?

Question

I have a dataframe as shown below:

id  value
100 a
100 b
100 c
100 d
200 1
200 2
200 3

How do I roll up to the below format?

id  value
100 ['a','b','c','d']
200 ['1','2','3']

Answer 1

You can groupby on 'id' and then apply list to value column and then call reset_index :

In [13]:

df.groupby('id')['value'].apply(list).reset_index()
Out[13]:
    id         value
0  100  [a, b, c, d]
1  200     [1, 2, 3]