python - How to find the number of the day in a year based on the actual dates using Pandas? -

my data frame data has date variable dateopen following format date_format = "%y-%m-%d %h:%m:%s.%f" , have new column called openday day number based on 365 days year. tried applying following

data['dateopen'] = [datetime.strptime(dt, date_format) dt in data['dateopen']] data['openday'] = [dt.day dt in data['dateopen']] 

however, day in month. example if date 2013-02-21 10:12:14.3 above formula return 21. however, want return 52 31 days january plus 21 days february.

is there simple way in pandas?

on latest pandas can use date-time properties:

>>> ts = pd.series(pd.to_datetime(['2013-02-21 10:12:14.3'])) >>> ts 0   2013-02-21 10:12:14.300000 dtype: datetime64[ns] >>> ts.dt.dayofyear 0    52 dtype: int64 

on older versions, may able convert datetimeindex , use .dayofyear property:

>>> pd.index(ts).dayofyear  # may work array([52], dtype=int32)