pandas add day to date and the number of day based on another column

Question

In python, my dataframe like:

date1 num
2017-03-02 8
2017-04-15 4
2017-06-30 1

I want the result dataframe(add date2 columns) like this:

date1 num date2
2017-03-02 8 2017-03-10
2017-04-15 4 2017-04-19
2017-06-30 1 2017-07-01

I know :df.date1 +pd.offsets.Day(x), but x is not allowed to be Series. And I know apply() function may could resolve this problem, but the lines of my dataframe is over one billion.

So what to do?

Answer 1

you can add timedeltas created by to_timedelta:

df['date2'] = df['date1'] + pd.to_timedelta(df['num'], unit='d')
print (df)
       date1  num      date2
0 2017-03-02    8 2017-03-10
1 2017-04-15    4 2017-04-19
2 2017-06-30    1 2017-07-01

If want add months use apply with axis=1 for proceses by rows and dateoffset:

df['date3'] = df.apply(lambda x: x['date1'] + pd.offsets.DateOffset(months=x['num']), 1)
print (df)
       date1  num      date3
0 2017-03-02    8 2017-11-02
1 2017-04-15    4 2017-08-15
2 2017-06-30    1 2017-07-30