How to build a datetime in dask from separate fields-CodePudding

I'm trying to build a computed column in dask, a datetime from separate fields year, month, day, hour. And I can't find a way to make it work.

With the method below it's creating a datetime column, but inside it's not datetime. I've tried different formulas, but none that work.

Python 3.8.10
- pandas==1.5.3
- dask==2023.1.1
- aiohttp==3.8.3

Get the data

    # data processing
    import dask.dataframe as dd
    
    # web data source
    url = "https://raw.githubusercontent.com/Rdatatable/data.table/master/vignettes/flights14.csv"
    
    # read demo data
    dtable = dd.read_csv(url)
    
    # print list of columns
    print('demo data list of fields : ',dtable.columns)

result:

demo data list of fields :  Index(['year', 'month', 'day',
'dep_delay', 'arr_delay', 'carrier', 'origin', 'dest', 'air_time',
'distance', 'hour'], dtype='object')

Then create the field. It looks like working, but no.

    # create datetime column from the 'year','month','day','hour' fields
    dtable['flight_datetime'] = dd.to_datetime( 
        (dtable.year *1000000 
          dtable.month*10000 
          dtable.day*100 
          dtable.hour).astype(str), format='%Y%m%d%H', errors='ignore')
    
    print('demo data list of fields : ',dtable.columns)
    print('demo data fields types : ',dtable.dtypes)
    print(dtable.flight_datetime.head())
    print(dtable.flight_datetime.dt.year.head())

result:

demo data list of fields :  Index(['year', 'month', 'day',
'dep_delay', 'arr_delay', 'carrier', 'origin', 'dest', 'air_time',
'distance', 'hour', 'flight_datetime'], dtype='object')

demo data fields types :
year                        int64
month                       int64
day                         int64
dep_delay                   int64
arr_delay                   int64
carrier                    object
origin                     object
dest                       object
air_time                    int64
distance                    int64
hour                        int64
flight_datetime    datetime64[ns]
dtype: object

0    2014010109
1    2014010111
2    2014010119
3    2014010107
4    2014010113
Name: flight_datetime, dtype: object

AttributeError: 'Series' object has no attribute 'year'

CodePudding user response：

As @RomanPerekhrest says in the comments, your not using the correct syntax for dd.to_datetime. The following is working for me:

dtable_time = dtable[['year','month','day','hour']]
dtable['flight_datetime'] = dd.to_datetime(dtable_time)

print('demo data list of fields : ', dtable.columns)
print('demo data fields types : ', dtable.dtypes)
print(dtable.flight_datetime.head())
print(dtable.flight_datetime.dt.year.head())

outputs:

demo data list of fields :  Index(['year', 'month', 'day', 'dep_delay', 'arr_delay', 'carrier', 'origin',
       'dest', 'air_time', 'distance', 'hour', 'flight_datetime'],
      dtype='object')
demo data fields types :  year                        int64
month                       int64
day                         int64
dep_delay                   int64
arr_delay                   int64
carrier                    object
origin                     object
dest                       object
air_time                    int64
distance                    int64
hour                        int64
flight_datetime    datetime64[ns]
dtype: object
0   2014-01-01 09:00:00
1   2014-01-01 11:00:00
2   2014-01-01 19:00:00
3   2014-01-01 07:00:00
4   2014-01-01 13:00:00
Name: flight_datetime, dtype: datetime64[ns]
0    2014
1    2014
2    2014
3    2014
4    2014
Name: flight_datetime, dtype: int64