您需要如果需要转换为datetime列time，请添加 to_datetime :

If need convert to datetime column time add to_datetime:

df['hour'] = pd.to_datetime(df['time']).dt.floor('H')
print (df)
                  time                hour
0  2017-02-10 00:00:00 2017-02-10 00:00:00
1  2017-02-10 00:01:00 2017-02-10 00:00:00
2  2017-02-10 00:02:00 2017-02-10 00:00:00
3  2017-02-10 00:03:00 2017-02-10 00:00:00
4   2017-12-1 10:05:00 2017-12-01 10:00:00
5   2017-12-1 10:06:00 2017-12-01 10:00:00