How to add new element to pandas.DataFrame column which is list?

Question

I have a pandas.DataFrame like this:

id       count        fruit_list
---------------------------------------
0        42           [orange, apple]
1        57           [lemon]
2        86           [kiwi]
3        33           [pineapple, pear]
4        11           [apple, lemon]
...

I need to add new string to fruit_list in every row. Let's say the string is banana , so I need to end with DataFrame like this:

id       count        fruit_list
---------------------------------------
0        42           [orange, apple, banana]
1        57           [lemon, banana]
2        86           [kiwi, banana]
3        33           [pineapple, pear, banana]
4        11           [apple, lemon, banana]
...

How can I do this most easily please?

Answer 1

Try apply :

df['fruit_list'] = df['fruit_list'].apply(lambda x: x + ['banana'])

Sample:

df = pd.DataFrame({'count': [42, 57], 
                   'fruit_list': [['orange', 'apple'], ['lemon']], 
                   'id': [0, 1]}).reindex_axis(['id','count','fruit_list'], 1)
print (df)
   id  count       fruit_list
0   0     42  [orange, apple]
1   1     57          [lemon]

df['fruit_list'] = df['fruit_list'].apply(lambda x: x + ['banana'])
print (df)
   id  count               fruit_list
0   0     42  [orange, apple, banana]
1   1     57          [lemon, banana]