v8-python

Python bindings for embedding V8 and running JavaScript, built on denoland/rusty_v8.

v8-python lets Python code create V8 isolates and contexts, evaluate JavaScript, pass values between Python and JavaScript, expose Python functions and classes to JavaScript, and install host APIs such as timers, console, module loading, and WebAssembly. It is implemented in Rust using denoland/rusty_v8.

Install

pip install v8-python

For local development:

uv run maturin develop

Tutorial

Run JavaScript

import v8

isolate = v8.Isolate()
builder = isolate.create_context_builder()
context = builder.build()

result = context.eval("'Hello' + ' from V8'")
print(result)

Expose a Python function

import v8

isolate = v8.Isolate()
builder = isolate.create_context_builder()


@builder.host_function(name="add")
def add(left: int, right: int) -> int:
    return left + right


context = builder.build()
print(context.eval("add(20, 22)"))

Install host APIs

Host APIs are installed through a profile. This keeps the context builder small and makes reusable runtime setups easy to share.

import v8

profile = v8.BaseProfile().install([v8.api.Timer()])

isolate = v8.Isolate()
builder = isolate.create_context_builder()
builder.use_profile(profile)
context = builder.build()

context.eval(
    """
    globalThis.events = [];
    setTimeout(() => events.push("ready"), 0);
    """
)

context.run_until_idle(max_tasks=10)
print(context.eval("events.join(', ')"))

Await a JavaScript Promise

JavaScript promises can be awaited from Python.

import asyncio
import v8

isolate = v8.Isolate()
builder = isolate.create_context_builder()
context = builder.build()


async def main():
    return await context.eval("Promise.resolve('done')")


print(asyncio.run(main()))

More focused examples are available in the examples/ directory.

Documentation

uv run --group doc zensical serve

License

MIT License.