[Python] Polars parse multiple datetime format [duplicate]

I have string column in polars dataframe with multiple datetime formats and I am using following code to convert datatype of column from string into datetime.

import polars as pl

df = pl.from_dict({'a': ["2025-11-17 11:51:44 UTC", "17.11.2025 11:51:44 UTC"]})

expr = (
pl.when(pl.col("a").str.starts_with("2025"))
.then(pl.col("a").str.to_datetime("%F %T %Z"))
.otherwise(pl.col("a").str.to_datetime("%d.%m.%Y %T %Z"))
.alias("a")
)

df.with_columns(expr)


However I am getting following error.


InvalidOperationError: conversion from `str` to `datetime[μs]` failed in column 'a' for 1 out of 2 values: ["17.11.2025 11:51:44 UTC"]

You might want to try:
- setting `strict=False` to set values that cannot be converted to `null`
- using `str.strptime`, `str.to_date`, or `str.to_datetime` and providing a format string


Is there anything missing I am here? Is is okay to pass expression with then and otherwise?

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