python pandas create a list group by value

Question

I have a dataframe in python:

    pID     sID     time 
0   2133    152414  2018-06-16
1   1721    152912  2018-06-17
2   2264    152912  2018-06-18

I want to create a new table with sID as the key and list of pID:

        pID time
152414 2133 2018-06-16
152912 1721 2018-06-17
       2264 2018-06-18

What is the best way to do it without iterating over all the dataframe? I tried:

df.pivot(index='sID', columns=['pID', 'time'])

But got:

ValueError: all arrays must be same length

For these table of 3 rows Thanks!

Answer 1

Try this:

import io
import pandas as pd

f = io.StringIO('''
2133    152414  2018-06-16
1721    152912  2018-06-17
2264    152912  2018-06-18''')

df = pd.read_csv(f, sep='\s+', header=None, names=['pID', 'sID', 'date'])
df.set_index(['sID', 'pID'])

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