在Panda Dataframe中对一系列列表进行分组

Question

I have a dataframe with a list in each cell. For each row of the dataframe I want to group over the 1st element of the lists and average the second element. Here some dummy data and a screenshot of the df to illustrate the problem:

import pandas as pd
df = pd.DataFrame({"Column A":[["Winter 2012",5],["Sommer 2012",10]],
                   "Column B":[["Sommer 2012",20],["Winter 2012",10]],
                   "Column C":[["Winter 2012",15],["Sommer 2012",30]]})
df

            Column A           Column B           Column C
0   [Winter 2012, 5]  [Sommer 2012, 20]  [Winter 2012, 15]
1  [Sommer 2012, 10]  [Winter 2012, 10]  [Sommer 2012, 30]

The desired output for the first line should look like this:

            Column D           Column E
0  [Winter 2012, 10]  [Sommer 2012, 20]
1  [Sommer 2012, 20]  [Winter 2012, 10]

Being completely new to Python, I simply cannot wrap my head around how to I could approach this.

Answer 1

Here's one way

In [410]: df.apply(lambda x: pd.Series(
                   x.apply(pd.Series)
                    .groupby(0, as_index=False, sort=False)
                    .mean()
                    .values.tolist(), index=['Column D', 'Column E']),
                   axis=1)
Out[410]:
            Column D           Column E
0  [Winter 2012, 10]  [Sommer 2012, 20]
1  [Sommer 2012, 20]  [Winter 2012, 10]