Search code examples
pythonlistpandascol

Pandas DataFrame: create a column from a list inside a column


I'm having the pandas DataFrame 'test_df':

email                      my_list
email1@email1.com          [1,9,3,5]
email2@email2.com          [6,3,3,15]
email3@email3.com          [7,7,2,5]
email4@email4.com          [5,5,5,5]

How can I have this following DataFrame (take the first 2 elem of 'my_list'):

email                      col1             col2             
email1@email1.com          1                9        
email2@email2.com          6                3
email3@email3.com          7                7
email4@email4.com          5                5           

I tried:

test_df['col1'] = test_df['my_list'][0]
test_df['col2'] = test_df['my_list'][1]

But it's not working


Solution

  • I asked a related question here, although I wanted to go a bit beyond expanding the lists into columns so the answers are more complicated than what you need. In your case, you can just do:

    # Using my own example data since it's a bit tough to copy-paste
    # a printed table and have the lists show up as lists
    df = pd.DataFrame({'email': ['email1@eg.com', 'email2@eg.com'], 
                       'lists': [[1, 9, 3, 5], [6, 3, 3, 15]]})
    df
    Out[14]: 
               email          lists
    0  email1@eg.com   [1, 9, 3, 5]
    1  email2@eg.com  [6, 3, 3, 15]
    
    objs = [df, pd.DataFrame(df['lists'].tolist()).iloc[:, :2]]
    pd.concat(objs, axis=1).drop('lists', axis=1)
    Out[13]: 
               email  0  1
    0  email1@eg.com  1  9
    1  email2@eg.com  6  3