Polars · Function

pl.last

pl.last returns the last column when called without names, or the last value from each named column when names are supplied.

How it works

pl.last produces an expression whose behavior depends on whether column names are supplied: without names it selects the final column in the current context; with names it selects the final value from each named column.

Syntax

polars.last(*columns: str) → Expr

Parameters

Name	Type	Description
`columns`	`str`	One or more column names.

Returns

Expr

Key points

Use pl.last to retrieve either the final column or terminal values, depending on whether names are passed.
The zero-argument form resolves the last column from the current selection context.
Passing names changes the result to the final value of every named column.
The function supports one or more positional column-name arguments.

Common mistakes

Calling pl.last() and calling pl.last with one or more names are different operations: the former returns a whole column, while the latter returns terminal values.

Example: Select the last column or values

import polars as pl

df = pl.DataFrame({
    "a": [1, 8, 3],
    "b": [4, 5, 2],
    "c": ["foo", "bar", "baz"],
})

print(df.select(pl.last()))
print(df.select(pl.last("a")))
print(df.select(pl.last("b", "c")))

The first selection returns the final column, while the other selections return the final value from each named column.

When to use it

Dynamic final-column selection

Selecting the rightmost column without hard-coding its name.

Final-value retrieval

Extracting terminal values from one or more known columns.

Multi-column summarization

Selecting several columns’ final values in one expression.

Interview questions

QHow does pl.last change behavior when column names are provided?

With no arguments, pl.last() returns an expression that takes the last column of the current context. With one or more column names, it takes the last value from each named column.

Follow-up: What does pl.last("b", "c") produce? It returns a one-row result containing the final value of both selected columns.

QWhat does the columns parameter represent?

The columns parameter accepts one or more column names. Supplying several names lets the expression retrieve the terminal value for each of those columns in one selection.

Follow-up: How would you select the final value from a dynamically chosen set of columns? Build the names programmatically and expand them as positional arguments when calling pl.last.

QWhat does the no-argument form return?

pl.last() is useful when the selection context itself determines which column is last. For example, selecting it from a DataFrame with columns a, b, and c returns column c with all its rows.

Follow-up: How does this differ from pl.col("c").last()? The latter explicitly targets column c and returns its final value, rather than selecting the final column wholesale.

polars.Expr.last
polars.col
polars.first

Source: polars.last — Polars documentation. Checked 2026-10-15.