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. 0.6.2 adds per-row usage and cost accounting, with token counts, latency, and cost_usd from an overridable price table.
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, per-row usage and cost
Pulls in mlx and mlx-lm; requires an Apple Silicon Mac and Python ≥ 3.10
Get started with a simple example
usage=True on inference_async and inference_messages (#76)
Pass usage=True to inference_async or inference_messages to get token counts, latency, and estimated cost per row alongside the response. It is useful for invoicing against LLM spend or surfacing usage to users. usage=False (the default) is byte-identical to before.
| Usage field | Type | Source |
|---|---|---|
| input_tokens | Int64 | Provider usage metadata, parsed for OpenAI, Groq, Anthropic, Gemini, and Bedrock |
| output_tokens | Int64 | Provider usage metadata |
| cached_tokens | Int64 | Anthropic's split cache counts are normalized so cached_tokens ⊆ input_tokens |
| latency_ms | Int64 | Measured around the HTTP call in Rust |
| cost_usd | Float64 | Computed from a packaged, overridable price table; null for unknown models |
price_table=, set_price_table(), register_model_price()
cost_usd is resolved against a price table shipped with the wheel (polar_llama/pricing.py plus polar_llama/data/prices.json). Override it per call with price_table= (a dict or a path), globally with set_price_table(...), or add one model with register_model_price(...). Unknown models yield cost_usd = null with a one-time warning rather than an error.
Local models: inference_local(..., usage=True) on the in-process MLX engine reports input_tokens, output_tokens, and latency_ms with cost_usd = 0.0. Caveats: Anthropic cache-write tokens are folded into input_tokens at the base input rate, so cost_usd slightly undercounts when prompt-cache writes occur, and usage=True combined with checkpoint= currently raises ValueError.
0.6.2 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, 0.6.1.
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 to 2026-07-14
| 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 |
| 0.6.1 | Checkpointing | checkpoint="path" / Checkpoint(...) on inference_async and inference_messages: resumable runs over a crash-durable Parquet store keyed by content + config hash |
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, usage, price_table) | Parallel async inference; plus prompt caching, checkpointing, usage/cost |
| inference(expr, *, provider, model, response_model) | Synchronous inference (deprecated in favor of inference_async) |
| inference_messages(expr, *, provider, model, response_model, cache, checkpoint, usage, price_table) | 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= |
| register_model_price(provider, model, *, input_per_1m, output_per_1m, cached_input_per_1m) / set_price_table(table) | Add or override prices used for cost_usd |
| col(...).llama.inference_local(*, model, system, engine, base_url, max_tokens, temperature, top_p, stop, usage, price_table) | 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.