> For the complete documentation index, see [llms.txt](https://docs.verygoodsecurity.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.verygoodsecurity.com/vault/developer-tools/larky/library-api/itertools.md).

# intertools

Starlark module for working with iterators library.

This module implements a number of iterator building blocks inspired by constructs from APL, Haskell, and SML. Each has been recast in a form suitable for Python. The module standardizes a core set of fast, memory efficient tools that are useful by themselves or in combination. Together, they form an “iterator algebra” making it possible to construct specialized tools succinctly and efficiently in pure Python.

Similar to [itertools in Python](https://docs.python.org/3/library/itertools.html).

## itertools.chain(\*iterables)

Make an iterator that returns elements from the first iterable until it is exhausted, then proceeds to the next iterable, until all of the iterables are exhausted. Used for treating consecutive sequences as a single sequence.

Example:

```python
chain(['ABC', 'DEF'], ['GHI'])
['ABC', 'DEF', 'GHI']
```

**Parameters:**

**iterables** - iterables to chain.

*Returns:* new iterable, that contains content of iterables.

## itertools.from\_iterable(iterables)

Alternate constructor for chain(). Gets chained inputs from a single iterable argument that is evaluated lazily. Same as chain()

**Parameters:**

**iterables** - iterables to chain.

*Returns:* new iterable, that contains content of iterables.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.verygoodsecurity.com/vault/developer-tools/larky/library-api/itertools.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.