Module polars_core::doc::time

DateTime related functionality

Polars supports most data types in Arrow related to time and dates. The datatypes that have most utility support are:

• Date32
  • A Date object representing the time in days since the unix epoch.
  • Chrono support type: NaiveDate
  • Underlying data type: i32
• Date64
  • A DateTime object representing the time in milliseconds since the unix epoch.
  • Chrono support type: NaiveDateTime
  • Underlying data type: i64

Utility methods

Given a Date32 or Date64 ChunkedArray one can extract various temporal information

Chrono

Polars has interopatibilty with the chrono library.

Example

use chrono::NaiveTime;
use polars_core::prelude::*;;

// We can create a ChunkedArray from NaiveTime objects
fn from_naive_time_to_time64(time_values: &[NaiveTime]) -> Time64NanosecondChunked {
    Time64NanosecondChunked::new_from_naive_time("name", time_values)
}

// Or from a ChunkedArray to NaiveTime objects
fn from_time64_to_naive_time(ca: &Time64NanosecondChunked) -> Vec<Option<NaiveTime>> {
    ca.as_naive_time()
}

String formatting

We can also directly parse strings given a predefined fmt: &str. This uses chrono’s NaiveTime::parse_from_str under the hood. So look there for the different formatting options. If the string parsing is not successful, the value will be None.

Examples

Parsing from Utf8Chunked

use polars_core::prelude::*;
use chrono::NaiveTime;

// String values to parse, Note that the 2nd value is not a correct time value.
let time_values = &["23:56:04", "26:00:99", "12:39:08"];
// Parsing fmt
let fmt = "%H:%M:%S";
// Create the ChunkedArray
let ca = Utf8Chunked::new_from_slice("time", time_values);
// Parse strings as DateTime objects
let date_ca = ca.as_date64(Some(fmt));

Parsing directly from slice

use polars_core::prelude::*;
use chrono::NaiveDateTime;

// String values to parse, Note that the 2nd value is not a correct time value.
let datetime_values = &[
            "1988-08-25 00:00:16",
            "2015-09-05 23:56:04",
            "2012-12-21 00:00:00",
        ];
// Parsing fmt
let fmt = "%Y-%m-%d %H:%M:%S";

// Create the ChunkedArray
let ca = Date64Chunked::parse_from_str_slice("datetime as ms since Epoch", datetime_values, fmt);

// or dates in different precision (days)
let ca = Date32Chunked::parse_from_str_slice("date as days since Epoch", datetime_values, fmt);