Retrieve date from datetime column in polars

Question

Currently when I try to retrieve date from a polars datetime column, I have to write sth. similar to:

df = pl.DataFrame({
    'time': [dt.datetime.now()]
})


df = df.select([
    pl.col("*"),
    pl.col("time").apply(lambda x: x.date()).alias("date")
])

Is there a different way, something closer to:

pl.col("time").dt.date().alias("date")

Asked By: Alex

||

Source

Answer 1

You can cast a Datetime column to a Date column:


import datetime
import polars as pl

df = pl.DataFrame({
    'time': [datetime.datetime.now()]
})

df.with_column(
    pl.col("time").cast(pl.Date)
)

shape: (1, 1)
┌────────────┐
│ time       │
│ ---        │
│ date       │
╞════════════╡
│ 2022-08-02 │
└────────────┘

Answered By: ritchie46

Answer 2

Since polars version 0.16.15 (released just a few days ago). The code in your question is actually valid.

pl.col("time").dt.date().alias("date")

This is the diff that made it possible. And it works both on pl.Series and pl.Expr (used in lazy data frames).

Answered By: Jan Kislinger

Retrieve date from datetime column in polars

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