# Locate where a behavior is implemented in Polars with Atlas in 2026

> Atlas helps Polars developers find the exact file and symbol responsible for a behavior, even when only knowing what the software does.

To locate where a behavior is implemented in a Polars codebase, Atlas combines semantic search, keyword grep, and LSP symbol graph analysis, allowing you to pinpoint the exact file and symbol responsible. This workflow integrates directly with your Polars development environment, leveraging tools like `pytest (assert_frame_equal)` for verification and `uv` for dependency management, ensuring a precise and efficient discovery process.

## Key takeaways

- Atlas uses semantic search, grep, and LSP to locate Polars behavior implementations.
- Semantic search understands natural language descriptions of Polars operations.
- `grep` provides precise keyword matching for Polars-specific code patterns.
- LSP tools enable navigation of the Polars symbol graph, finding references and declarations.
- Atlas ensures safety with permission-gated tools and unified diff review for Polars code changes.

## How Atlas Pinpoints Polars Behavior Implementations

Atlas employs a three-pronged approach to locate Polars behavior implementations, fusing semantic and keyword retrieval with symbol graph analysis. This hybrid strategy ensures that in 2026, you can find code even when your natural language description doesn't match exact keywords in the source.

When you need to find the precise location of a behavior in a Polars project, Atlas attacks the problem from three complementary angles. First, the `codebase_search` tool uses a semantic index built from AST declarations via tree-sitter, allowing it to understand the meaning of your query even if the exact words are not present in the code. This is particularly useful in Polars, where the expression API often abstracts underlying operations. Second, the `grep` tool provides exact text matching, powered by `ripgrep`, which is crucial for confirming specific string patterns or variable names. Finally, the `lsp` tool leverages the Language Server Protocol to work through the symbol graph, enabling you to jump to declarations or find all references to a Polars function or method. This combined approach, fused by reciprocal rank fusion, ensures comprehensive and accurate code discovery.

## Describing Polars Behavior for Semantic Search

To initiate a search for Polars behavior, you describe the functionality in natural language to Atlas's `codebase_search` tool. This semantic search capability, available in 2026, understands your intent even if the code uses different terminology, providing a powerful starting point.

When you know what a Polars operation does but not its exact function name, you can describe the behavior to Atlas using the `codebase_search` tool. For instance, you might ask, 'Where does Polars handle predicate pushdown for `scan_csv` operations?' Atlas, having indexed your codebase by AST declarations, can return candidate declarations that semantically match your description, even if the terms 'predicate pushdown' or 'scan_csv' aren't explicitly in the function's docstring or name. This is invaluable for navigating complex Polars `LazyFrame` chains and understanding where optimizations like projection pruning occur, as Atlas can read your `pyproject.toml` to understand the project context and dependencies.

## Confirming Polars Code Locations with Grep

After an initial semantic search, you can confirm potential Polars code locations using the `grep` tool, which offers precise keyword matching. This tool, powered by `ripgrep`, allows you to apply real regex patterns and path filters to narrow down results to specific Polars files or directories in 2026.

Once `codebase_search` provides a set of candidate declarations for a Polars behavior, the `grep` tool allows you to confirm and refine these findings with exact text matching. You can use `grep` with a regular expression to search for specific Polars function calls, method names, or even comments. For example, if you suspect a particular `collect()` call is materializing a `LazyFrame` too early, you could `grep` for `\.collect\(` within specific Polars source files. The tool supports `include` and `path` filters, enabling you to target searches to relevant areas of your project, such as `polars/src/expressions` or `polars/src/io`, ensuring you quickly find the exact lines of code.

## Navigating Polars Code with LSP Tools

Atlas integrates LSP tools to provide a rich symbol graph experience for Polars code, allowing you to jump directly to declarations or find all references. This capability ensures that in 2026, you can efficiently explore the call path of any Polars function or method.

With a strong candidate file identified, Atlas's `read` tool allows you to open the best match. If you make a wrong guess, Atlas provides a 'File not found' error with a 'Did you mean' list, preventing wasted effort. Once inside the file, the `lsp` tool becomes indispensable for Polars development. You can use `lsp findReferences` to see every callsite of a specific Polars function or method, helping you understand its usage across your project. Alternatively, `lsp workspaceSymbol` lets you jump directly to the declaration of a symbol by name, which is perfect for exploring the Polars expression API or understanding how a `scan_csv` operation is implemented. This deep integration with the symbol graph helps you trace the flow of data and operations within your `LazyFrame` chains.

## Reviewing and Approving Code Changes in Polars Projects

Atlas prioritizes safety and transparency when suggesting or making changes to your Polars codebase, ensuring every action is permission-gated. In 2026, Atlas drafts a read-only plan and presents a unified diff for approval before any file is written, giving you full control.

Atlas is designed with multiple layers of safety to ensure you maintain full control over your Polars codebase. Every Atlas tool call is permission-gated, requiring your explicit `allow`, `ask`, or `deny` before execution. When Atlas drafts a plan, it does so in a read-only plan agent, asking for your approval before switching to a build agent that can modify files. For any proposed edit, Atlas computes a unified diff and surfaces it for your approval, allowing you to review changes to your Polars code, such as converting a `scan_csv` plus filter into a lazy chain. Atlas also snapshots file changes as git patches, so edits can be easily diffed, rolled back, or staged and committed on your behalf. If Atlas runs `pytest (assert_frame_equal)` or formats code with `ruff format`, these actions are also behind permission prompts, and any resulting diffs are presented for your review.

## Steps

1. Start Atlas in your Polars project directory, ensuring your `pyproject.toml` pins Polars correctly for context.
2. Describe the Polars behavior you want to locate using `atlas codebase_search "Where does Polars handle predicate pushdown for scan_csv?"` to get initial semantic candidates.
3. Refine the search with `atlas grep "\.collect\("` using a regular expression and path filters like `--include 'polars/src/**/*.rs'` to confirm specific code patterns.
4. Open the most promising candidate file with `atlas read polars/src/io/csv/mod.rs` to inspect its contents directly.
5. Use `atlas lsp findReferences 'CsvReader::new'` to see all callsites of a Polars function, or `atlas lsp workspaceSymbol 'LazyFrame::collect'` to jump to its declaration.
6. Summarize the call path and implementation details back to yourself, noting concrete file and line references within the Polars codebase.
7. If you've made any changes or want to verify behavior, ask Atlas to run your Polars tests with `atlas run pytest (assert_frame_equal)` behind a permission prompt.
8. Should any code be modified, allow Atlas to format the diff with `ruff format` and review the changes before committing them to your Polars project.

## FAQ

### How does Atlas understand Polars-specific code and its expression API?

Atlas indexes your Polars codebase using AST declarations via tree-sitter, allowing it to understand the structure and meaning of your code, including complex `LazyFrame` chains and the expression API. This semantic understanding helps Atlas provide relevant results even when your query doesn't use exact function names.

### Can Atlas find code even if I don't know the exact Polars function name?

Yes, Atlas's `codebase_search` tool is designed for this. You can describe the Polars behavior in natural language, and Atlas will use its semantic index to find candidate declarations that match the meaning, even if the specific function or method name is unknown to you.

### What if Atlas suggests the wrong file in my Polars project?

Atlas provides multiple layers of refinement. After an initial `codebase_search`, you can use `grep` with specific regex patterns and path filters to narrow down results. If you `read` a file and it's incorrect, Atlas will loudly fail with 'File not found' and suggest alternatives, ensuring you don't waste time on bad paths.

### How does Atlas ensure I approve changes to my Polars code?

Atlas operates with strict safety protocols. All tool calls are permission-gated, and any plan to modify files is first drafted in a read-only agent. Before writing any changes to your Polars codebase, Atlas computes and presents a unified diff for your explicit approval, and can snapshot changes as git patches for easy rollback.

### Can Atlas integrate with my existing Polars test suite and formatting tools?

Absolutely. Atlas can run `pytest (assert_frame_equal)` behind a permission prompt to verify changes in your Polars project. It can also format code diffs using `ruff format`, ensuring your codebase adheres to your team's style guidelines, all while presenting these actions for your approval.

### Does Atlas keep my Polars code private when performing searches?

Yes, Atlas prioritizes privacy. It can build its code index using local Ollama embeddings, which means your Polars source code never leaves your machine or goes to third-party servers. All processing and indexing happen locally, keeping your proprietary code secure.

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