Python Pandas 从另一列的列表中删除一列列表中的项目

Question

I have a dataframe with two columns that both contain lists of strings. df['col1'] and df['col2]. I am trying to remove in each row all the items contained in col2's list from col1's list and make a new column. For example:

col1           col2         col3
[a, b, c]     [a, b]        [c]
[a, c, f, d]  [a, f]        [c, d]    
[d, c, e, f]  [d, e, f, c]  []

Answer 1

You can create your own function to create the new lists and then use apply on the dataframe to execute the function for each row like so:

import pandas as pd

df = pd.DataFrame({'col1':[['a', 'b', 'c'], ['a', 'c', 'f', 'd'], ['d', 'c', 'e', 'f']], 
                   'col2':[['a', 'b'], ['a', 'f'], ['d', 'e', 'f', 'c']]})

def func(df):
    return list(set(df['col1']) - set(df['col2']))

df['col3'] = df.apply(func, axis = 1)

The function converts the lists to sets and uses set subtraction to remove values contained in col2 from col1 .