How to create additional columns weekofyear,month and dayofweek in polars?-CodePudding

I am trying to create additional columns from an existing column name in polars. The existing column name is starttime. This column contains datetime.

starttime	endtime	storageid	volume_id	avgiops
2022-02-10 09:32:20	2022-02-10 09:34:28	TUNYKYPG72	4c8d6c31	27
2022-02-10 10:34:10	2022-02-10 10:35:12	TUNYKYPG42	4c8d6d31	34

From this table , I would like to create additional columns like weekofyear,dayofweek,year etc.

pl_df.with_column(pl.col('starttime').str.strptime(pl.Date, fmt='%Y').cast(pl.Datetime)).alias
("year")

But it fails as

exceptions.ComputeError: strict conversion to dates failed, maybe set strict=False

In pyspark ,we can create it like below

df_dates = pl.select(
        [
            weekofyear("starttime").alias("week"),
            dayofweek("starttime").alias("weekday"),
            hour("starttime").alias("hour"),
            dayofmonth("starttime").alias("day"),
            to_date("starttime").alias("collectiontime"),
            starttime,endtime,storageid,volume_id,avgiops])

How to create additional columns weekofyear,dayofweek,month in polars?

CodePudding user response：

You can .strptime(pl.Datetime) then use the various methods in the .dt namespace.

df.with_columns(
   pl.col("starttime").str.strptime(pl.Datetime)
).with_columns([
   pl.col("starttime").dt.week().alias("week"),
   pl.col("starttime").dt.weekday().alias("weekday"),
   pl.col("starttime").dt.hour().alias("hour"),
   pl.col("starttime").dt.day().alias("day"),
])

shape: (2, 9)
┌─────────────────────┬─────────────────────┬────────────┬───────────┬─────────┬──────┬─────────┬──────┬─────┐
│ starttime           | endtime             | storageid  | volume_id | avgiops | week | weekday | hour | day │
│ ---                 | ---                 | ---        | ---       | ---     | ---  | ---     | ---  | --- │
│ datetime[μs]        | str                 | str        | str       | i64     | u32  | u32     | u32  | u32 │
╞═════════════════════╪═════════════════════╪════════════╪═══════════╪═════════╪══════╪═════════╪══════╪═════╡
│ 2022-02-10 09:32:20 | 2022-02-10 09:34:28 | TUNYKYPG72 | 4c8d6c31  | 27      | 6    | 4       | 9    | 10  │
├─────────────────────┼─────────────────────┼────────────┼───────────┼─────────┼──────┼─────────┼──────┼─────┤
│ 2022-02-10 10:34:10 | 2022-02-10 10:35:12 | TUNYKYPG42 | 4c8d6d31  | 34      | 6    | 4       | 10   | 10  │
└─────────────────────┴─────────────────────┴────────────┴───────────┴─────────┴──────┴─────────┴──────┴─────┘