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Python bindings for the Y-CRDT built from yrs (Rust)

Project description

PyPI version


Ypy is a Python binding for Y-CRDT. It provides distributed data types that enable real-time collaboration between devices. Ypy can sync data with any other platform that has a Y-CRDT binding, allowing for seamless cross-domain communication. The library is a thin wrapper around Yrs, taking advantage of the safety and performance of Rust.

🧪 Project is still experimental. Expect the API to change before a version 1.0 stable release.


pip install y-py

Getting Started

Ypy provides many of the same shared data types as Yjs. All objects are shared within a YDoc and get modified within a transaction block.

import y_py as Y

d1 = Y.YDoc()
# Create a new YText object in the YDoc
text = d1.get_text('test')
# Start a transaction in order to update the text
with d1.begin_transaction() as txn:
    # Add text contents
    text.extend(txn, "hello world!")

# Create another document
d2 = Y.YDoc()
# Share state with the original document
state_vector = Y.encode_state_vector(d2)
diff = Y.encode_state_as_update(d1, state_vector)
Y.apply_update(d2, diff)

value = str(d2.get_text('test'))

assert value == "hello world!"

Development Setup

  1. Install Rust and Python
  2. Install maturin in order to build Ypy: pip install maturin
  3. Create a development build of the library: maturin develop


All tests are located in /tests. To run the tests, install pytest and run the command line tool from the project root:

pip install pytest

Using Hatch

If you are using hatch, there is a test environment matrix defined in pyproject.toml that will run commands in virtual environments for py37 through py312.

hatch run test:maturin develop
hatch run test:pytest

Build Ypy

Build the library as a wheel and store them in target/wheels:

maturin build

Ypy in WASM (Pyodide)

As a Rust-based library, Ypy cannot build "pure Python" wheels. CI processes build and upload a number of wheels to PyPI, but PyPI does not support hosting emscripten / wasm32 wheels necessary to import in Pyodide (see for more info and updates). For now, Ypy will build emscripten wheels and attach the binaries as assets in the appropriate Releases entry. Unfortunately, trying to install directly from the Github download link will result in a CORS error, so you'll need to use a proxy to pull in the binary and write / install from emscripten file system or host the binary somewhere that is CORS accessible for your application.

You can try out Ypy in Pyodide using the terminal emulator at

Welcome to the Pyodide terminal emulator 🐍
Python 3.10.2 (main, Sep 15 2022 23:28:12) on WebAssembly/Emscripten
Type "help", "copyright", "credits" or "license" for more information.
>>> wheel_url = ''
>>> wheel_name = wheel_url.split('/')[-1]
>>> wheel_name
>>> proxy_url = f'{wheel_url}'
>>> proxy_url
>>> import pyodide
>>> resp = await pyodide.http.pyfetch(proxy_url)
>>> resp.status
>>> content = await resp.bytes()
>>> len(content)
>>> content[:50]
>>> with open(wheel_name, 'wb') as f:
...   f.write(content)
>>> import micropip
>>> await micropip.install(f'emfs:./{wheel_name}')
>>> import y_py as Y
>>> Y
<module 'y_py' from '/lib/python3.10/site-packages/y_py/'>
>>> d1 = Y.YDoc()
>>> text = d1.get_text('test')
>>> with d1.begin_transaction() as txn:
    text.extend(txn, "hello world!")
>>> d2 = Y.YDoc()
>>> state_vector = Y.encode_state_vector(d2)
>>> diff = Y.encode_state_as_update(d1, state_vector)
>>> Y.apply_update(d2, diff)
>>> d2.get_text('test')
YText(hello world!)

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