Anthropic Python API library

The Anthropic Python library provides convenient access to the Anthropic REST API from any Python 3.7+ application. It includes type definitions for all request params and response fields, and offers both synchronous and asynchronous clients powered by httpx.

For the AWS Bedrock API, see anthropic-bedrock.

Documentation

The API documentation can be found here.

Installation

pip install anthropic

Usage

The full API of this library can be found in api.md.

from anthropic import Anthropic, HUMAN_PROMPT, AI_PROMPT

anthropic = Anthropic(
    # defaults to os.environ.get("ANTHROPIC_API_KEY")
    api_key="my api key",
)

completion = anthropic.completions.create(
    model="claude-2.1",
    max_tokens_to_sample=300,
    prompt=f"{HUMAN_PROMPT} how does a court case get to the Supreme Court?{AI_PROMPT}",
)
print(completion.completion)

While you can provide an api_key keyword argument, we recommend using python-dotenv to add ANTHROPIC_API_KEY="my-anthropic-api-key" to your .env file so that your API Key is not stored in source control.

Async usage

Simply import AsyncAnthropic instead of Anthropic and use await with each API call:

from anthropic import AsyncAnthropic, HUMAN_PROMPT, AI_PROMPT

anthropic = AsyncAnthropic(
    # defaults to os.environ.get("ANTHROPIC_API_KEY")
    api_key="my api key",
)


async def main():
    completion = await anthropic.completions.create(
        model="claude-2.1",
        max_tokens_to_sample=300,
        prompt=f"{HUMAN_PROMPT} how does a court case get to the Supreme Court?{AI_PROMPT}",
    )
    print(completion.completion)


asyncio.run(main())

Functionality between the synchronous and asynchronous clients is otherwise identical.

Streaming Responses

We provide support for streaming responses using Server Side Events (SSE).

from anthropic import Anthropic, HUMAN_PROMPT, AI_PROMPT

anthropic = Anthropic()

stream = anthropic.completions.create(
    prompt=f"{HUMAN_PROMPT} Your prompt here{AI_PROMPT}",
    max_tokens_to_sample=300,
    model="claude-2.1",
    stream=True,
)
for completion in stream:
    print(completion.completion, end="", flush=True)

The async client uses the exact same interface.

from anthropic import AsyncAnthropic, HUMAN_PROMPT, AI_PROMPT

anthropic = AsyncAnthropic()

stream = await anthropic.completions.create(
    prompt=f"{HUMAN_PROMPT} Your prompt here{AI_PROMPT}",
    max_tokens_to_sample=300,
    model="claude-2.1",
    stream=True,
)
async for completion in stream:
    print(completion.completion, end="", flush=True)

Streaming Helpers

This library provides several conveniences for streaming messages, for example:

import asyncio
from anthropic import AsyncAnthropic

client = AsyncAnthropic()

async def main() -> None:
    async with client.beta.messages.stream(
        max_tokens=1024,
        messages=[
            {
                "role": "user",
                "content": "Say hello there!",
            }
        ],
        model="claude-2.1",
    ) as stream:
        async for text in stream.text_stream:
            print(text, end="", flush=True)
        print()

    message = await stream.get_final_message()
    print(message.model_dump_json(indent=2))

asyncio.run(main())

Streaming with client.beta.messages.stream(...) exposes various helpers for your convenience including event handlers and accumulation.

Alternatively, you can use client.beta.messages.create(..., stream=True) which only returns an async iterable of the events in the stream and thus uses less memory (it does not build up a final message object for you).

Token counting

You can estimate billing for a given request with the client.count_tokens() method, eg:

client = Anthropic()
client.count_tokens('Hello world!')  # 3

Using types

Nested request parameters are TypedDicts. Responses are Pydantic models, which provide helper methods for things like:

• Serializing back into JSON, model.model_dump_json(indent=2, exclude_unset=True)
• Converting to a dictionary, model.model_dump(exclude_unset=True)

Typed requests and responses provide autocomplete and documentation within your editor. If you would like to see type errors in VS Code to help catch bugs earlier, set python.analysis.typeCheckingMode to basic.

Handling errors

When the library is unable to connect to the API (for example, due to network connection problems or a timeout), a subclass of anthropic.APIConnectionError is raised.

When the API returns a non-success status code (that is, 4xx or 5xx response), a subclass of anthropic.APIStatusError is raised, containing status_code and response properties.

All errors inherit from anthropic.APIError.

import anthropic

client = anthropic.Anthropic()

try:
    client.completions.create(
        prompt=f"{anthropic.HUMAN_PROMPT} Your prompt here{anthropic.AI_PROMPT}",
        max_tokens_to_sample=300,
        model="claude-2.1",
    )
except anthropic.APIConnectionError as e:
    print("The server could not be reached")
    print(e.__cause__)  # an underlying Exception, likely raised within httpx.
except anthropic.RateLimitError as e:
    print("A 429 status code was received; we should back off a bit.")
except anthropic.APIStatusError as e:
    print("Another non-200-range status code was received")
    print(e.status_code)
    print(e.response)

Error codes are as followed:

Retries

Certain errors are automatically retried 2 times by default, with a short exponential backoff. Connection errors (for example, due to a network connectivity problem), 408 Request Timeout, 409 Conflict, 429 Rate Limit, and >=500 Internal errors are all retried by default.

You can use the max_retries option to configure or disable retry settings:

from anthropic import Anthropic, HUMAN_PROMPT, AI_PROMPT

# Configure the default for all requests:
anthropic = Anthropic(
    # default is 2
    max_retries=0,
)

# Or, configure per-request:
anthropic.with_options(max_retries=5).completions.create(
    prompt=f"{HUMAN_PROMPT} Can you help me effectively ask for a raise at work?{AI_PROMPT}",
    max_tokens_to_sample=300,
    model="claude-2.1",
)

Timeouts

By default requests time out after 10 minutes. You can configure this with a timeout option, which accepts a float or an httpx.Timeout object:

from anthropic import Anthropic, HUMAN_PROMPT, AI_PROMPT

# Configure the default for all requests:
anthropic = Anthropic(
    # default is 10 minutes
    timeout=20.0,
)

# More granular control:
anthropic = Anthropic(
    timeout=httpx.Timeout(60.0, read=5.0, write=10.0, connect=2.0),
)

# Override per-request:
anthropic.with_options(timeout=5 * 1000).completions.create(
    prompt=f"{HUMAN_PROMPT} Where can I get a good coffee in my neighbourhood?{AI_PROMPT}",
    max_tokens_to_sample=300,
    model="claude-2.1",
)

On timeout, an APITimeoutError is thrown.

Note that requests that time out are retried twice by default.

Default Headers

We automatically send the anthropic-version header set to 2023-06-01.

If you need to, you can override it by setting default headers per-request or on the client object.

Be aware that doing so may result in incorrect types and other unexpected or undefined behavior in the SDK.

from anthropic import Anthropic

client = Anthropic(
    default_headers={"anthropic-version": "My-Custom-Value"},
)

Advanced

Logging

We use the standard library logging module.

You can enable logging by setting the environment variable ANTHROPIC_LOG to debug.

$ export ANTHROPIC_LOG=debug

How to tell whether None means null or missing

In an API response, a field may be explicitly null, or missing entirely; in either case, its value is None in this library. You can differentiate the two cases with .model_fields_set:

if response.my_field is None:
  if 'my_field' not in response.model_fields_set:
    print('Got json like {}, without a "my_field" key present at all.')
  else:
    print('Got json like {"my_field": null}.')

Accessing raw response data (e.g. headers)

The "raw" Response object can be accessed by prefixing .with_raw_response. to any HTTP method call.

from anthropic import Anthropic, HUMAN_PROMPT, AI_PROMPT

anthropic = Anthropic()

response = anthropic.completions.with_raw_response.create(
    model="claude-2.1",
    max_tokens_to_sample=300,
    prompt=f"{HUMAN_PROMPT} how does a court case get to the Supreme Court?{AI_PROMPT}",
)
print(response.headers.get('X-My-Header'))

completion = response.parse()  # get the object that `completions.create()` would have returned
print(completion.completion)

These methods return an APIResponse object.

Configuring the HTTP client

You can directly override the httpx client to customize it for your use case, including:

• Support for proxies
• Custom transports
• Additional advanced functionality

import httpx
from anthropic import Anthropic

client = Anthropic(
    # Or use the `ANTHROPIC_BASE_URL` env var
    base_url="http://my.test.server.example.com:8083",
    http_client=httpx.Client(
        proxies="http://my.test.proxy.example.com",
        transport=httpx.HTTPTransport(local_address="0.0.0.0"),
    ),
)

Managing HTTP resources

By default the library closes underlying HTTP connections whenever the client is garbage collected. You can manually close the client using the .close() method if desired, or with a context manager that closes when exiting.

Versioning

This package generally follows SemVer conventions, though certain backwards-incompatible changes may be released as minor versions:

1. Changes that only affect static types, without breaking runtime behavior.
2. Changes to library internals which are technically public but not intended or documented for external use. (Please open a GitHub issue to let us know if you are relying on such internals).
3. Changes that we do not expect to impact the vast majority of users in practice.

We take backwards-compatibility seriously and work hard to ensure you can rely on a smooth upgrade experience.

We are keen for your feedback; please open an issue with questions, bugs, or suggestions.

Requirements

Python 3.7 or higher.