Remove 'seconds' and 'minutes' from a Pandas dataframe column

Solution 1:

dt.round

This is how it should be done... use dt.round

df.assign(Date=df.Date.dt.round('H'))

                 Date       Num
0 2011-01-01 00:00:00  0.577957
1 2011-01-01 01:00:00  0.995748
2 2011-01-01 02:00:00  0.864013
3 2011-01-01 03:00:00  0.468762
4 2011-01-01 04:00:00  0.866827

OLD ANSWER

One approach is to set the index and use resample

df.set_index('Date').resample('H').last().reset_index()

                 Date       Num
0 2011-01-01 00:00:00  0.577957
1 2011-01-01 01:00:00  0.995748
2 2011-01-01 02:00:00  0.864013
3 2011-01-01 03:00:00  0.468762
4 2011-01-01 04:00:00  0.866827

Another alternative is to strip the date and hour components

df.assign(
    Date=pd.to_datetime(df.Date.dt.date) +
         pd.to_timedelta(df.Date.dt.hour, unit='H'))

                 Date       Num
0 2011-01-01 00:00:00  0.577957
1 2011-01-01 01:00:00  0.995748
2 2011-01-01 02:00:00  0.864013
3 2011-01-01 03:00:00  0.468762
4 2011-01-01 04:00:00  0.866827