serialx 1.2.1

Serial library with native async support for Windows and POSIX

Introduction

Serialx is a no-compromise serial communication library for Python targeting common platforms such as Linux (POSIX), macOS, and Windows. It provides both synchronous and native asynchronous APIs for all platforms.

Installation

pip install serialx

For drop-in import compatibility (serial, serial_asyncio, serial_asyncio_fast) without runtime patching, install:

pip install serialx-compat

Usage

Serialx features a pyserial and pyserial-asyncio compatibility layer for easy testing. As early as possible, run serialx.patch_pyserial() and it will provide API-compatible replacements.

import serialx
serialx.patch_pyserial()

# These will now use serialx
import serial
import serial_asyncio

Serialx features a familiar synchronous API:

import serialx

with serialx.Serial("/dev/serial/by-id/port", baudrate=115200) as serial:
    data = serial.readexactly(5)
    serial.write(b"test")

    serial.set_modem_pins(rts=True, dtr=True)
    pins = serial.get_modem_pins()
    assert pins.rts is serialx.PinState.HIGH
    assert pins.dtr is serialx.PinState.HIGH

A high-level asynchronous serial (reader, writer) pair:

import asyncio
import contextlib

import serialx

async def main():
	reader, writer = await serialx.open_serial_connection("/dev/serial/by-id/port", baudrate=115200)

	with contextlib.closing(writer):
	    data = await reader.readexactly(5)
	    writer.write(b"test")
	    await writer.drain()

And a low-level asynchronous serial transport:

import asyncio
import serialx

async def main():
	loop = asyncio.get_running_loop()
	protocol = YourProtocol()

	transport, protocol = await serialx.create_serial_connection(
	    loop,
	    lambda: protocol,
	    url="/dev/serial/by-id/port",
	    baudrate=115200
	)

	await transport.set_modem_pins(rts=True, dtr=True)

ESPHome serial proxy

Serialx can communicate with serial devices exposed by ESPHome.

It can either create the API instance directly, for simplicity:

from serialx import open_serial_connection

reader, writer = await open_serial_connection(
    url="esphome://192.168.1.42:6053/?port_name=Zigbee&noise_psk=...",
    baudrate=115200,
)

Or reuse an existing API instance, for efficiency:

from aioesphomeapi import APIClient
from serialx import open_serial_connection
from serialx.platforms.serial_esphome import ESPHomeSerialTransport

# An external API instance
api = APIClient(address="192.168.1.42", port=6053, noise_psk="...", password=None)
await api.connect(login=True)

reader, writer = await open_serial_connection(
    url=None,
    transport_cls=ESPHomeSerialTransport,
    api=api,
    port_name="Zigbee",
    baudrate=115200,
)

Development

All development dependencies are listed in pyproject.toml. To install them, use:

uv pip install '.[dev]'

On macOS and Windows, a Rust toolchain is required to build the native serial port enumeration extension. Install Rust via rustup.

Set up pre-commit hooks with pre-commit install. Your code will then be type checked and auto-formatted when you run git commit. You can do this on-demand with pre-commit run.

Serialx relies on automated testing. CI runs tests using both socat virtual PTYs (Linux/macOS) and socket-based serial pairs. To also test with physical adapter pairs, pass CLI flags to pytest:

pytest --adapter-pair=/dev/serial/by-id/left1:/dev/serial/by-id/right1 \
       --adapter-pair=/dev/serial/by-id/left2:/dev/serial/by-id/right2

By default, tests run in parallel. You can disable this by passing -n 0 to pytest.