Message Batches API — Python

The Batches API (`POST /v1/messages/batches`) processes Messages API requests asynchronously at 50% of standard prices.

Key Facts

Up to 100,000 requests or 256 MB per batch
Most batches complete within 1 hour; maximum 24 hours
Results available for 29 days after creation
50% cost reduction on all token usage
All Messages API features supported (vision, tools, caching, etc.)

Create a Batch

```python import anthropic from anthropic.types.message_create_params import MessageCreateParamsNonStreaming from anthropic.types.messages.batch_create_params import Request

client = anthropic.Anthropic()

message_batch = client.messages.batches.create( requests=[ Request( custom_id="request-1", params=MessageCreateParamsNonStreaming( model="{{OPUS_ID}}", max_tokens=16000, messages=[{"role": "user", "content": "Summarize climate change impacts"}] ) ), Request( custom_id="request-2", params=MessageCreateParamsNonStreaming( model="{{OPUS_ID}}", max_tokens=16000, messages=[{"role": "user", "content": "Explain quantum computing basics"}] ) ), ] )

print(f"Batch ID: {message_batch.id}") print(f"Status: {message_batch.processing_status}") ```

Poll for Completion

```python import time

while True: batch = client.messages.batches.retrieve(message_batch.id) if batch.processing_status == "ended": break print(f"Status: {batch.processing_status}, processing: {batch.request_counts.processing}") time.sleep(60)

print("Batch complete!") print(f"Succeeded: {batch.request_counts.succeeded}") print(f"Errored: {batch.request_counts.errored}") ```

Retrieve Results

Note: Examples below use `match/case` syntax, requiring Python 3.10+. For earlier versions, use `if/elif` chains instead.

```python for result in client.messages.batches.results(message_batch.id): match result.result.type: case "succeeded": msg = result.result.message text = next((b.text for b in msg.content if b.type == "text"), "") print(f"[{result.custom_id}] {text[:100]}") case "errored": if result.result.error.type == "invalid_request": print(f"[{result.custom_id}] Validation error - fix request and retry") else: print(f"[{result.custom_id}] Server error - safe to retry") case "canceled": print(f"[{result.custom_id}] Canceled") case "expired": print(f"[{result.custom_id}] Expired - resubmit") ```

Cancel a Batch

```python cancelled = client.messages.batches.cancel(message_batch.id) print(f"Status: {cancelled.processing_status}") # "canceling" ```

Batch with Prompt Caching

```python shared_system = [ {"type": "text", "text": "You are a literary analyst."}, { "type": "text", "text": large_document_text, # Shared across all requests "cache_control": {"type": "ephemeral"} } ]

message_batch = client.messages.batches.create( requests=[ Request( custom_id=f"analysis-{i}", params=MessageCreateParamsNonStreaming( model="{{OPUS_ID}}", max_tokens=16000, system=shared_system, messages=[{"role": "user", "content": question}] ) ) for i, question in enumerate(questions) ] ) ```

Full End-to-End Example

```python import anthropic import time from anthropic.types.message_create_params import MessageCreateParamsNonStreaming from anthropic.types.messages.batch_create_params import Request

client = anthropic.Anthropic()

1. Prepare requests

items_to_classify = [ "The product quality is excellent!", "Terrible customer service, never again.", "It's okay, nothing special.", ]

requests = [ Request( custom_id=f"classify-{i}", params=MessageCreateParamsNonStreaming( model="{{HAIKU_ID}}", max_tokens=50, messages=[{ "role": "user", "content": f"Classify as positive/negative/neutral (one word): {text}" }] ) ) for i, text in enumerate(items_to_classify) ]

2. Create batch

batch = client.messages.batches.create(requests=requests) print(f"Created batch: {batch.id}")

3. Wait for completion

while True: batch = client.messages.batches.retrieve(batch.id) if batch.processing_status == "ended": break time.sleep(10)

4. Collect results

results = {} for result in client.messages.batches.results(batch.id): if result.result.type == "succeeded": msg = result.result.message results[result.custom_id] = next((b.text for b in msg.content if b.type == "text"), "")

for custom_id, classification in sorted(results.items()): print(f"{custom_id}: {classification}") ```

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