A Python library for parallel LLM inference across providers, built on Polars DataFrames.
Polar Llama is a Python library that enables parallel inference calls to multiple Large Language Model providers through Polars dataframes. It streamlines batch processing of AI queries without serial request delays, making it ideal for data-intensive AI applications. 0.6.1 makes large batch runs resumable: pass checkpoint= and a job that dies halfway picks up where it left off.
Send multiple inference requests in parallel without waiting for individual completions
OpenAI, Anthropic, Gemini, Groq, AWS Bedrock, and on-device MLX (Apple Silicon)
Dataframe-native tool calling: emission, batch-parallel execution, and synthesis are all ordinary columns
Built for long batch jobs: token streaming, resumable checkpoints
Pulls in mlx and mlx-lm; requires an Apple Silicon Mac and Python ≥ 3.10
Get started with a simple example
inference_async(..., checkpoint="path") and inference_messages (#75)
Large jobs fail mid-run because of rate limits, network blips, and provider outages. Pass checkpoint="path" to inference_async or inference_messages and completed rows are persisted to a sidecar Parquet store as the run progresses. Re-run the same code and it resumes, skipping rows that already finished, so a job killed at 50% costs about one full pass. The API stays a lazy, DataFrame-shaped Polars expression that composes in with_columns / LazyFrame pipelines.
| Checkpoint option | Default | Meaning |
|---|---|---|
| path | (required) | Sidecar directory of Parquet parts plus _meta.json; created if missing |
| flush_every | 100 | Unique pending rows sent (and flushed to disk) per chunk; bounds re-spend after a crash to one chunk |
| retry_failed | True | Re-attempt rows stored as failed on resume; False returns the stored error instead |
| on_mismatch | "restart" | What to do when the store's fingerprint doesn't match the current config: "restart" or "error" |
Content keys hash the row and the whole run configuration
Each row is keyed by a sha256 content hash over the row input plus the full run configuration: provider, model, system prompt, response schema, and the endpoint base-URL override. Change any of them and old entries never match, so you can’t get a stale result from a different configuration. Hashing uses hashlib.sha256 rather than Polars’ seed- and version-unstable Expr.hash(), so resume survives library upgrades.
The store is crash-durable: each flush writes a uniquely named .tmp part and atomically renames it, so a crash mid-write leaves nothing a reader will pick up. Structured outputs and tool-use passes work unchanged. The hashing primitives live in polar_llama/keys.py so content-hash caching can reuse them.
0.6.1 is cumulative: every feature shipped in 0.2.2 is still here, plus everything added across 0.3.0, 0.5.0, 0.5.1, 0.5.2, 0.5.3, 0.6.0.
Released 2026-06-10 to 2026-07-12
tools_to_response_model, mcp_tools, execute_tool_calls, tool_results_to_message: batch-parallel tool calling over an MCP server or a Python executor (0.3.0)
cache=True / CacheConfig shares a cached system prefix across rows via Anthropic cache_control, with 5-minute and 1-hour TTLs (0.3.0)
Signature, Predict, evaluate, BootstrapFewShot, InstructionOptimizer: DSPy-style instruction and few-shot tuning (0.3.0)
inference_local with server and in_process engines, collapsed prefix prefill, batched quantized KV cache (0.5.0), and an on-device prompt-tuning bridge (0.5.1)
Along the way: updated default models for every provider, OPENAI_BASE_URL / ANTHROPIC_BASE_URL overrides and POLAR_LLAMA_MAX_CONCURRENCY (0.3.0), and fixes for in-process Gemma 3n inference (0.5.2). See the 0.5.2 docs for the full details.
Released 2026-07-13
tag_taxonomy() works on OpenAI strict mode again. The per-field thinking reasoning is now List[{value, reasoning}] instead of a dict keyed by value name, and $ref sibling keywords are stripped from generated schemas (#51). A new warning flags Dict-typed fields in user-supplied response models.
Released 2026-07-13
| Release | Feature | What shipped |
|---|---|---|
| 0.6.0 | Streaming | inference_stream() with an on_token(row_index, delta) callback and a Struct{text, finished} column; native SSE for OpenAI, Groq, Anthropic; GROQ_BASE_URL override |
The agent loop unrolled into ordinary dataframe columns
Declare a task, then let an optimizer tune instructions or mine few-shot demos
Features from earlier releases for long, expensive batch jobs
Batched generation via mlx-lm, no API keys, no network
Process customer feedback at scale
Generate embeddings, then find nearest neighbors with HNSW
Classify documents with reasoning, reflection, and confidence scores
Six inference targets: five hosted providers plus on-device MLX
Default model: gpt-4o-mini
Default model: claude-opus-4-8; supports cache=True for prompt caching
Default model: us.anthropic.claude-haiku-4-5-20251001-v1:0; region resolved from AWS_REGION / AWS_DEFAULT_REGION
Default model: gemini-2.5-flash; native system_instruction and JSON-schema structured outputs
Default model: llama-3.3-70b-versatile; GROQ_BASE_URL overrides the endpoint (0.6.0+)
No API key, no network: the server engine points at a local OpenAI-compatible endpoint, and in_process drives mlx-lm directly
Core expressions exported from polar_llama
| Function | Purpose |
|---|---|
| inference_async(expr, *, provider, model, response_model, cache, system_prompt, checkpoint) | Parallel async inference; plus prompt caching, checkpointing |
| inference(expr, *, provider, model, response_model) | Synchronous inference (deprecated in favor of inference_async) |
| inference_messages(expr, *, provider, model, response_model, cache, checkpoint) | Multi-turn conversation inference over JSON or List(Struct) message arrays |
| inference_stream(expr, *, provider, model, on_token, messages) | Token-by-token streaming; returns Struct{text, finished} per row |
| string_to_message(expr, *, message_type) | Convert text to a {role, content} message |
| combine_messages(*exprs) | Merge message columns/arrays into one ordered conversation |
| tag_taxonomy(expr, taxonomy, *, provider, model) | Classify text against a taxonomy with reasoning, reflection, and confidence |
| embedding_async(expr, *, provider, model) | Parallel embedding generation (OpenAI, Gemini, Bedrock) |
| cosine_similarity / dot_product / euclidean_distance(vec1, vec2) | Rust-powered vector similarity metrics |
| knn_hnsw(query_expr, reference_expr, *, k) | Stateless approximate nearest-neighbor search via HNSW |
| mcp_tools(transport, *, timeout_s) | Fetch tool definitions from an MCP server (tools/list) |
| tools_to_response_model(tools, *, model_name) | Build a Pydantic emission schema so the LLM emits structured tool calls |
| execute_tool_calls(expr, *, transport, executor, tools, concurrency, timeout_s) | Run every emitted call of every row in parallel; failures are data |
| tool_results_to_message(expr, *, role) | Render tool results as a message for the synthesis inference pass |
| Signature / Predict / evaluate / BootstrapFewShot / InstructionOptimizer | DSPy-style prompt optimization engine (polar_llama.optimize) |
| Checkpoint(path, *, flush_every, retry_failed, on_mismatch) | Checkpoint store configuration for checkpoint= |
| col(...).llama.inference_local(*, model, system, engine, base_url, max_tokens, temperature, top_p, stop) | On-device inference on Apple Silicon via mlx-lm |
| polar_llama.local.make_local_inference_fn(model, *, engine, collapse, max_tokens, ...) | Build an inference_fn that backs the optimizer with on-device Gemma 3n |
Every expression is also available on the fluent .llama namespace (pl.col("text").llama.inference_async(...), .llama.to_message(...), .llama.embedding(...), .llama.inference_stream(...), and so on).
Set up your API keys and overrides in a .env file:
Share a cached system prefix across rows (Anthropic cache_control):
Run tests with configured providers:
Process large datasets with AI insights: sentiment analysis, classification, entity extraction with validated structured outputs
Resume after crashes, track spend per row, and never pay twice for the same request
Let the LLM call databases, internal APIs, or MCP servers at scale, with every call, result, and retry as an ordinary dataframe column
Run classification, extraction, or tuning on local models with no API keys and no data leaving the machine
Licensed under MIT.
Questions or issues? Open one on GitHub.