Python pandas adding an extra column and filling it with 0

Question

I have a dataframe in python I did a groupby on, and it contains data per month. It looks like when I extract an exact year:

month	data
1	15
2	24
3	15
4	29
5	55
6	4
7	19
8	10
9	15
10	32
11	53
12	20

However sometimes, it has missing data like:

month	data
1	15
2	24
3	15
4	29
5	55
6	4
7	19
8	10
9	15
11	53
12	20

So I was wondering a way to fill in the missing data (10 in this case) and making the default value 0.

I tried to use reindex, but that doesn't fill columns only indexes and I can't find an alternative for column based operations.

Answer 1

I would like to use resample to do the grouping on datetime.