Eager sequence creation
Create a contiguous or stepped integer Series for immediate Python-side use.
Polars · Function
pl.arange
pl.arange generates an integer range with an inclusive start and exclusive end. It returns an expression by default or an eagerly evaluated Series when eager=True.
How it works
pl.arange produces integer values from an inclusive start up to, but not including, an exclusive end, advancing by step. By default it returns a lazy expression; eager=True evaluates it immediately as a Series, and dtype controls the integer type.
Syntax
polars.arange(start: int | IntoExprColumn = 0, end: int | IntoExprColumn | None = None, step: int = 1, *, dtype: PolarsIntegerType | DataTypeExpr = Int64, eager: bool = False) → Expr | SeriesParameters
| Name | Type | Description |
|---|---|---|
start | int | IntoExprColumn | Inclusive lower bound; defaults to 0. |
end | int | IntoExprColumn | None | Exclusive upper bound; defaults to None. |
step | int | Increment between values; defaults to 1. |
dtype | PolarsIntegerType | DataTypeExpr | Output data type; defaults to Int64. |
eager | bool | Whether to evaluate immediately; defaults to False. |
Returns
Expr or SeriesColumn of integer data type dtype.
Key points
- Use pl.arange to construct integer sequences.
- The function is an alternate name for int_range.
- The start value belongs to the range when the sequence reaches it.
- step determines the distance between consecutive generated integers.
- Use dtype to choose the output integer type.
- Setting eager=True evaluates the range immediately as a Series.
Common mistakes
- The default returns an expression rather than a Series, so use eager=True when immediate evaluation is required.
- The end value is not included in the generated range.
Example: Create an integer Series
import polars as pl
values = pl.arange(0, 6, 2, eager=True)
print(values)
Creates an eager Series containing 0, 2, and 4.
When to use it
Lazy expression construction
Build an integer-range expression as part of a Polars query.
Typed integer ranges
Generate values with an explicitly selected Polars integer dtype.
Interview questions
QWhat does pl.arange return by default?
pl.arange generates an integer range with an inclusive start and exclusive end. Its default result is an Expr, while eager=True evaluates immediately and returns a Series.
Follow-up: How would you generate values with a different integer type? Pass the desired Polars integer dtype through dtype.
QHow are range boundaries and increments interpreted?
The start parameter sets the inclusive lower bound, end sets the exclusive upper bound, and step controls the increment. If end is omitted, the function can still accept the documented range inputs through its expression-oriented API.
Follow-up: What boundary behavior should tests verify? They should confirm that start is present when reachable and end is absent.
QHow does pl.arange relate to other Polars range functions?
pl.arange is an alias for int_range, so both names represent integer-range generation. int_ranges is the related function for generating a range independently for each input row.
Follow-up: Which related function is intended for row-wise ranges? Use int_ranges rather than a single shared range.
Related
int_rangeint_ranges