Cartesia Python API library

The Cartesia Python library provides convenient access to the Cartesia REST API from any Python 3.9+ application. The library includes type definitions for all request params and response fields, and offers both synchronous and asynchronous clients powered by httpx.

It is generated with Stainless.

Documentation

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

Installation

# install from PyPI
pip install '--pre cartesia'

Usage

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

from cartesia import Cartesia

client = Cartesia(
    api_key="My API Key",
)

page = client.voices.list()
print(page.data)

Async usage

Simply import AsyncCartesia instead of Cartesia and use await with each API call:

import asyncio
from cartesia import AsyncCartesia

client = AsyncCartesia(
    api_key="My API Key",
)


async def main() -> None:
    page = await client.voices.list()
    print(page.data)


asyncio.run(main())

Functionality between the synchronous and asynchronous clients is otherwise identical.

Examples

We have extensive examples in examples/examples.py (and examples/async_examples.py), including:

• tts_generate_to_file: generate text-to-speech audio and save it to a file.
• tts_websocket_basic: connect to Cartesia over websockets and generate text-to-speech audio
• tts_websocket_continuations: stream transcripts to Cartesia over websockets. This is useful when your text is generated by an LLM's streaming API.
• tts_async_concurrent_contexts: multiple concurrently-generated text-to-speech audios streamed over a single websocket. This is the most performant way to integrate Cartesia at scale.

With aiohttp

By default, the async client uses httpx for HTTP requests. However, for improved concurrency performance you may also use aiohttp as the HTTP backend.

You can enable this by installing aiohttp:

# install from PyPI
pip install '--pre cartesia[aiohttp]'

Then you can enable it by instantiating the client with http_client=DefaultAioHttpClient():

import asyncio
from cartesia import DefaultAioHttpClient
from cartesia import AsyncCartesia


async def main() -> None:
    async with AsyncCartesia(
        api_key="My API Key",
        http_client=DefaultAioHttpClient(),
    ) as client:
        page = await client.voices.list()
        print(page.data)


asyncio.run(main())

Using types

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

• Serializing back into JSON, model.to_json()
• Converting to a dictionary, model.to_dict()

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.

Pagination

List methods in the Cartesia API are paginated.

This library provides auto-paginating iterators with each list response, so you do not have to request successive pages manually:

from cartesia import Cartesia

client = Cartesia()

all_voices = []
# Automatically fetches more pages as needed.
for voice in client.voices.list():
    # Do something with voice here
    all_voices.append(voice)
print(all_voices)

Or, asynchronously:

import asyncio
from cartesia import AsyncCartesia

client = AsyncCartesia()


async def main() -> None:
    all_voices = []
    # Iterate through items across all pages, issuing requests as needed.
    async for voice in client.voices.list():
        all_voices.append(voice)
    print(all_voices)


asyncio.run(main())

Alternatively, you can use the .has_next_page(), .next_page_info(), or .get_next_page() methods for more granular control working with pages:

first_page = await client.voices.list()
if first_page.has_next_page():
    print(f"will fetch next page using these details: {first_page.next_page_info()}")
    next_page = await first_page.get_next_page()
    print(f"number of items we just fetched: {len(next_page.data)}")

# Remove `await` for non-async usage.

Or just work directly with the returned data:

first_page = await client.voices.list()

print(f"next page cursor: {first_page.starting_after}")  # => "next page cursor: ..."
for voice in first_page.data:
    print(voice.id)

# Remove `await` for non-async usage.

Nested params

Nested parameters are dictionaries, typed using TypedDict, for example:

from cartesia import Cartesia

client = Cartesia()

access_token = client.access_token.create(
    grants={},
)
print(access_token.grants)

File uploads

Request parameters that correspond to file uploads can be passed as bytes, or a PathLike instance or a tuple of (filename, contents, media type).

from pathlib import Path
from cartesia import Cartesia

client = Cartesia()

client.datasets.files.upload(
    id="id",
    file=Path("/path/to/file"),
)

The async client uses the exact same interface. If you pass a PathLike instance, the file contents will be read asynchronously automatically.

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 cartesia.APIConnectionError is raised.

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

All errors inherit from cartesia.APIError.

import cartesia
from cartesia import Cartesia

client = Cartesia()

try:
    client.voices.list()
except cartesia.APIConnectionError as e:
    print("The server could not be reached")
    print(e.__cause__)  # an underlying Exception, likely raised within httpx.
except cartesia.RateLimitError as e:
    print("A 429 status code was received; we should back off a bit.")
except cartesia.APIStatusError as e:
    print("Another non-200-range status code was received")
    print(e.status_code)
    print(e.response)

Error codes are as follows:

Status Code	Error Type
400	BadRequestError
401	AuthenticationError
403	PermissionDeniedError
404	NotFoundError
422	UnprocessableEntityError
429	RateLimitError
>=500	InternalServerError
N/A	APIConnectionError

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 cartesia import Cartesia

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

# Or, configure per-request:
client.with_options(max_retries=5).voices.list()

Timeouts

By default requests time out after 1 minute. You can configure this with a timeout option, which accepts a float or an httpx.Timeout object:

from cartesia import Cartesia

# Configure the default for all requests:
client = Cartesia(
    # 20 seconds (default is 1 minute)
    timeout=20.0,
)

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

# Override per-request:
client.with_options(timeout=5.0).voices.list()

On timeout, an APITimeoutError is thrown.

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

Default Headers

We automatically send the cartesia-version header set to 2025-11-04.

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

from cartesia import Cartesia

client = Cartesia(
    default_headers={"cartesia-version": "My-Custom-Value"},
)

Advanced

Logging

We use the standard library logging module.

You can enable logging by setting the environment variable CARTESIA_LOG to info.

$ export CARTESIA_LOG=info

Or to debug for more verbose logging.

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, e.g.,

from cartesia import Cartesia

client = Cartesia()
response = client.voices.with_raw_response.list()
print(response.headers.get('X-My-Header'))

voice = response.parse()  # get the object that `voices.list()` would have returned
print(voice.id)

These methods return an APIResponse object.

The async client returns an AsyncAPIResponse with the same structure, the only difference being awaitable methods for reading the response content.

.with_streaming_response

The above interface eagerly reads the full response body when you make the request, which may not always be what you want.

To stream the response body, use .with_streaming_response instead, which requires a context manager and only reads the response body once you call .read(), .text(), .json(), .iter_bytes(), .iter_text(), .iter_lines() or .parse(). In the async client, these are async methods.

with client.voices.with_streaming_response.list() as response:
    print(response.headers.get("X-My-Header"))

    for line in response.iter_lines():
        print(line)

The context manager is required so that the response will reliably be closed.

Making custom/undocumented requests

This library is typed for convenient access to the documented API.

If you need to access undocumented endpoints, params, or response properties, the library can still be used.

Undocumented endpoints

To make requests to undocumented endpoints, you can make requests using client.get, client.post, and other http verbs. Options on the client will be respected (such as retries) when making this request.

import httpx

response = client.post(
    "/foo",
    cast_to=httpx.Response,
    body={"my_param": True},
)

print(response.headers.get("x-foo"))

Undocumented request params

If you want to explicitly send an extra param, you can do so with the extra_query, extra_body, and extra_headers request options.

Undocumented response properties

To access undocumented response properties, you can access the extra fields like response.unknown_prop. You can also get all the extra fields on the Pydantic model as a dict with response.model_extra.

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 cartesia import Cartesia, DefaultHttpxClient

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

You can also customize the client on a per-request basis by using with_options():

client.with_options(http_client=DefaultHttpxClient(...))

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.

from cartesia import Cartesia

with Cartesia() as client:
  # make requests here
  ...

# HTTP client is now closed

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.

Determining the installed version

If you've upgraded to the latest version but aren't seeing any new features you were expecting then your python environment is likely still using an older version.

You can determine the version that is being used at runtime with:

import cartesia
print(cartesia.__version__)

Migrating from 2.x

The 3.x series of this library maintains backwards compatibility with the method signatures from the 2.x version. To use the latest helpers, see MIGRATING.md.

Requirements

Python 3.9 or higher.

Contributing

See the contributing documentation.