LM Studio Python SDK

Using the SDK

Installation

The SDK can be installed from PyPI as follows:

$ pip install lmstudio

Examples

The base component of the LM Studio SDK is the (synchronous) Client. This should be created once and used to manage the underlying websocket connections to the LM Studio instance.

However, a top level convenience API is provided for convenience in interactive use (this API implicitly creates a default Client instance which will remain active until the Python interpreter is terminated).

Using this convenience API, requesting text completion from an already loaded LLM is as straightforward as:

import lmstudio as lms

model = lms.llm()
model.complete("Once upon a time,")

Requesting a chat response instead only requires the extra step of setting up a Chat helper to manage the chat history and include it in response prediction requests:

import lmstudio as lms

EXAMPLE_MESSAGES = (
    "My hovercraft is full of eels!",
    "I will not buy this record, it is scratched."
)

model = lms.llm()
chat = lms.Chat("You are a helpful shopkeeper assisting a foreign traveller")
for message in EXAMPLE_MESSAGES:
    chat.add_user_message(message)
    print(f"Customer: {message}")
    response = model.respond(chat)
    chat.add_assistant_response(response)
    print(f"Shopkeeper: {response}")

TODO: Refer readers to the SDK documentation for more info.

Contributing to SDK development

Fetching the source code

$ git clone https://github.com/lmstudio-ai/lmstudio-python
$ cd lmstudio-python

To be able to run tox -e sync-sdk-schema, it is also necessary to ensure the lmstudio-js submodule is updated:

$ git submodule update --init --recursive

Development Environment

In order to work on the Python SDK, you need to install :pypi:pdm, :pypi:tox, and :pypi:tox-pdm (everything else can be executed via tox environments).

Given these tools, the default development environment can be set up and other commands executed as described below.

The simplest option for handling that is to install uv, and then use its uv tool command to set up pdm and a second environment with tox + tox-pdm. pipx is another reasonable option for this task.

In order to use the Python SDK, you just need some form of Python environment manager (since lmstudio-python publishes the package lmstudio to PyPI).

Recommended local checks

The set of checks recommended for local execution are accessible via the check marker in tox:

$ tox -m check

This runs the same checks as the static and test markers (described below).

Code consistency checks

The project source code is autoformatted and linted using :pypi:ruff. It also uses :pypi:mypy in strict mode to statically check that Python APIs are being accessed as expected.

All of these commands can be invoked via tox:

$ tox -e format

$ tox -e lint

$ tox -e typecheck

Linting and type checking can be executed together using the static marker:

$ tox -m static

Avoid using # noqa comments to suppress these warnings - wherever possible, warnings should be fixed instead. # noqa comments are reserved for rare cases where the recommended style causes severe readability problems, and there isn't a more explicit mechanism (such as typing.cast) to indicate which check is being skipped.

# fmt: off/on and # fmt: skip comments may be used as needed when the autoformatter makes readability worse instead of better (for example, collapsing lists to a single line when they intentionally cover multiple lines, or breaking alignment of end-of-line comments).

Automated testing

The project's tests are written using the :pypi:pytest test framework. :pypi:tox is used to automate the setup and execution of these tests across multiple Python versions. One of these is nominated as the default test target, and is accessible via the test marker:

$ tox -m test

You can also use other defined versions by specifying the target environment directly:

$ tox -e py3.11

There are additional labels defined for running the oldest test environment, the latest test environment, and all test environments:

$ tox -m test_oldest
$ tox -m test_latest
$ tox -m test_all

To ensure all the required models are loaded before running the tests, run the following command:

$ tox -e load-test-models

tox has been configured to forward any additional arguments it is given to pytest. This enables the use of pytest's rich CLI. In particular, you can select tests using all the options that pytest provides:

$ # Using file name
$ tox -m test -- tests/test_basics.py
$ # Using markers
$ tox -m test -- -m "slow"
$ # Using keyword text search
$ tox -m test -- -k "catalog"

Additional notes on running and updating the tests can be found in the tests/README.md file.

Expanding the API

• the content of src/lmstudio/_sdk_models is automatically generated by the sync-sdk-schema.py script in sdk-schema and should not be modified directly. Run tox -e sync-sdk-schema to regenerate the Python submodule from the existing export of the lmstudio-js schema (for example, after modifying the data model template). Run tox -e sync-sdk-schema -- --regen-schema after updating the sdk-schema/lmstudio-js submodule itself to a newer iteration of the lmstudio-js JSON API.
• as support for new API namespaces is added to the SDK, each should get a dedicated session type (similar to those for the already supported namespaces), even if it is only used privately by the client implementation.
• as support for new API channel endppoints is added to the SDK, each should get a dedicated base endpoint type (similar to those for the already supported channels). This avoids duplicating the receive message processing between the sync and async APIs.
• the json_api.SessionData base class is useful for defining rich result objects which offer additional methods that call back into the SDK (for example, this is how downloaded model listings offer their interfaces to load a new instance of a model).