Dropping column gives unexpected result

Question

I have a list of dataframes

df1 = {'col1': ['a', 'a', 'b', 'c', 'c', 'd'], '2020': [3, 4, 3, 8, 4, 5]}
df2 = {'col1': ['a', 'a', 'b', 'c', 'c', 'd'], '2021': [30, 40, 30, 80, 40, 50]}
df3 = {'col1': ['a', 'a', 'b', 'c', 'c', 'd'], '2022': [31, 41, 31, 81, 41, 51]}

listOfDf = [df1, df2, df3]

Then I add them side by side

sideBySideDataframe = pd.concat(listOfDf , axis=1)

Which gives me this

    2020    col1    2021    col1    2022    col1
0   3       'a'     30      'a'     31      'a'
1   4       'a'     40      'a'     41      'a'
2   3       'b'     30      'b'     31      'b'
3   8       'c'     80      'c'     81      'c'
... 

Now, I only want to keep col1 once. So I tried to delete col1 by index

sideBySideDataframe = sideBySideDataframe.drop(sideBySideDataframe.columns[[1, 3]],axis = 1)

However, this deleted me all col1 columns. I tried

sideBySideDataframe = sideBySideDataframe.drop(sideBySideDataframe.columns[[1]],axis = 1)

with the same effect. However, when I use

sideBySideDataframe = sideBySideDataframe.set_index('col1')

I get

                  2020   2021   2022
col1
('a', 'a', 'a')   ...
('a', 'a', 'a')
('b', 'b', 'b')
('c', 'c', 'c') 

My output should be

                  2020   2021   2022
col1
'a'               ...
'a'
'b'
'c'

Sooo, I am not sure why pandas deletes all col1 , even if I only reference col1 by index . Is there a way to only keep one duplicated column name when doing pd.concat(listOfDf, axis=1) or how would I set the index, so that it does not add all the values from each column where the name fits col1 .

Answer 1

I'd say you set col1 as index, then concat:

sideBySideDataframe = pd.concat([d.set_index('col1') for d in listOfDf], axis=1)

Output:

      2020  2021  2022
col1                  
a        3    30    31
a        4    40    41
b        3    30    31
c        8    80    81
c        4    40    41
d        5    50    51