index.py

import os
import sys
import json
from time import sleep

# if we open the fd before bun has written to it
# we'll get a "bad fd" error :\
sleep(1)

fd = 3
read_pipe = os.fdopen(fd, "r")
write_pipe = os.fdopen(fd, "w")

def read():
    line = read_pipe.readline()
    print("[py]: bun -> py -> @raw", line.encode())

    # TMP: fix bun bug - @see https://github.com/oven-sh/bun/issues/13799
    if len(line) > 0 and line[0] == "\x01":
        line = line[1:]
    line = line.strip()

    if not line:
        sys.exit(0)

    msg = json.loads(line)
    print("[py]: bun -> py -> @json", msg)
    return msg

def write(msg):
    print("[py]: py -> bun", msg)
    write_pipe.write(json.dumps(msg) + "\n")
    write_pipe.flush()

while True:
    try:
        msg = read()
        write("msg recvd")
    except EOFError:
        break

index.ts

import { spawn } from 'bun'

const proc = spawn({
  cmd: ['python3', 'index.py'],
  serialization: 'json',
  stdio: ['inherit', 'inherit', 'inherit'],
  ipc(msg) {
    console.log('[bun] py -> bun:', msg)
  },
  onExit(subprocess, exitCode, signalCode, error) {
    console.log('python process ended with exit code', exitCode, signalCode)
    if (error) console.error(error)
  },
})

function send(msg: any) {
  console.log('[bun] bun -> py:', msg)
  proc.send(msg)
}

send('0 mark')

setTimeout(() => {
  send('2000 mark')
}, 2000)

setTimeout(() => {
  send('4000 mark')
}, 4000)