How can I use the apply() function for a single column?

Question

I have a pandas dataframe with multiple columns. I want to change the values of the only the first column without affecting the other columns. How can I do that using apply() in pandas?

Answer 1

Given a sample dataframe df as:

   a  b
0  1  2
1  2  3
2  3  4
3  4  5

what you want is:

df['a'] = df['a'].apply(lambda x: x + 1)

that returns:

   a  b
0  2  2
1  3  3
2  4  4
3  5  5