# `range`

The `range()` built-in represents an immutable sequence of numbers (or any object that implements the **index** dunder method). Used in the [markdown][markdown] to control the number of loops while iterating through a passed-in line or list. Used in [robot-simulator][robot-simulator] to represent the values from zero to 3 as assigned to NORTH, EAST, SOUTH, WEST.

TODO: ADD MORE DETAIL

See the Python documentation entries for the [immutable][immutable] [`range` type][docs-range-type] and its [constructor][range-as-function]. This is Python's most commonly used tool for efficiently working with a [sequential collection][docs-sequence-types] of [`int`][int] values.

[immutable]: https://github.com/exercism/v3/blob/main/reference/concepts/immutability.md
[docs-range-type]: https://docs.python.org/3/library/stdtypes.html#typesseq-range
[docs-range-as-function]: https://docs.python.org/3/library/stdtypes.html#range
[docs-sequence-types]: https://docs.python.org/3/library/stdtypes.html#typesseq
[markdown]: ../../exercise-concepts/markdown.md
[robot-simulator]: ../../exercise-concepts/robot-simulator.md
