Repeating particular row of pandas dataframe

Question

I want to repeat a specific row of pandas data frame for a given number of times.

For example, this is my data frame

df= pd.DataFrame({
'id' : ['1','1', '2', '2','2','3'],
'val' : ['2015_11','2016_2','2011_9','2011_11','2012_2','2018_2'],
'data':['a','a','b','b','b','c']
})

print(df)

Here, "Val" column contains date in string format. It has a specific pattern 'Year_month'. For the same "id", I want the rows repeated the number of times that is equivalent to the difference between the given "val" column values. All other columns except the val column should have the duplicated value of previous row.

The output should be:

Please read Under what circumstances may I add “urgent” or other similar phrases to my question, in order to obtain faster answers? - the summary is that this is not an ideal way to address volunteers, and is probably counterproductive to obtaining answers. Please refrain from adding this to your questions. — halfer
– halfer, Commented Aug 25, 2018 at 7:31

user3483203 · Accepted Answer · 2018-08-25 05:44:47Z

3

Using resample:

df.val = pd.to_datetime(df.val, format='%Y_%m')
out = df.set_index('val').groupby('id').data.resample('1m').ffill().reset_index()
out.assign(val=out.val.dt.strftime('%Y_%m'))

   id      val data
0   1  2015_11    a
1   1  2015_12    a
2   1  2016_01    a
3   1  2016_02    a
4   2  2011_09    b
5   2  2011_10    b
6   2  2011_11    b
7   2  2011_12    b
8   2  2012_01    b
9   2  2012_02    b
10  3  2018_02    c

answered Aug 25, 2018 at 5:44

user3483203

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