bootstrapping code for launching python from electron when packaged inside pyinstaller directory structure

index.js

import { app, BrowserWindow, Menu, MenuItem, globalShortcut } from 'electron';
const {ipcMain} = require('electron');  // do not use ipcRenderer in main process, use ipcMain
const path = require('path')
const url = require('url')
const log = require('electron-log');  // https://www.npmjs.com/package/electron-log
const sh = require("shelljs");  // https://github.com/shelljs/shelljs 

log.transports.file.level = 'debug';  // transports: console and file, levels: error, warn, info, verbose, debug, silly
log.transports.console.level = 'warn';

log.debug('--------------------- APP START -------------------------------')
log.debug('index.js main process')
log.debug('cwd is', sh.pwd().stdout);

// DEPLOYMENT SUPPORT
const PY_DIST_FOLDER = '../dist'  // now lives above
const PY_FOLDER = '..'
const PY_MODULE = 'api_pythermal' // without .py suffix


const guessPackaged = () => {
  const fullPath = path.join(__dirname, PY_DIST_FOLDER)
  // console.log('looking for dist directory here', fullPath)
  // log.info('looking for dist directory here', fullPath)
  return require('fs').existsSync(fullPath)
}

const createPyProc = () => {
  let script = getScriptPath()
  let port = '' + selectPort()

  // console.log('script', script, 'port', port, 'guessPackaged', guessPackaged())
  log.debug('script', script, 'port', port, 'guessPackaged', guessPackaged())

  // enhancement to provide Python with critical env vars
  let extra_env = {
    NODE_ENV: 'production',
    LANG: 'en_AU.UTF-8',
    PYTHONUNBUFFERED: '1',
    PYTHONDONTWRITEBYTECODE: '1',
    EXAMPLE_VAR: 'hey there'
  }
  // makes a copy of existing env, such that it is, and adds to it
  let options = {
    env : Object.assign({}, process.env, extra_env),
    cwd: sh.pwd().stdout
  }

  if (guessPackaged()) {
    pyProc = require('child_process').execFile(script, [port], options)
  }
  else {
    delete options.NODE_ENV;  // don't want in production
    let python_path = sh.which('python').stdout  // this will return null if no python found
    log.debug('which virtual python', python_path)
    pyProc = require('child_process').spawn(python_path, [script, port], options)
  }

  if (pyProc != null) {
    // console.log('child process success on port ' + port)
    log.debug('child process success on port ' + port)
  }

  pyProc.stdout.on('data', function (data) {
    // console.log('stdout: ' + data.toString());
    log.debug('stdout: ' + data.toString().trim());
  });
  pyProc.stderr.on('data', function (data) {
    // console.log('stderr: ' + data.toString());
    log.debug('stderr: ' + data.toString().trim());
  });

  pyProc.on('exit', function (code) {
    if (code == null)
      log.debug('python exited with null code - WTF?')
    else {
      // console.log('child process exited with code ' + code.toString());
      log.debug('child process exited with code ' + code.toString());
    }
    python_is_dead = true  // just in case need to send before main render windows set up
    if (mainWindow == null)
      log.debug('Cannot send a message to renderer window that python has exited')
    else
      mainWindow.webContents.send('python_exited_notice')  // for all other cases
  });

}

const exitPyProc = () => {
  pyProc.kill()
  pyProc = null
  pyPort = null
}

app.on('ready', createPyProc)
app.on('will-quit', exitPyProc)


const getScriptPath = () => {
  if (!guessPackaged()) {
    return path.join(__dirname, PY_FOLDER, PY_MODULE + '.py')
  }
  if (process.platform === 'win32') {
    return path.join(__dirname, PY_DIST_FOLDER, PY_MODULE, PY_MODULE + '.exe')
  }
  return path.join(__dirname, PY_DIST_FOLDER, PY_MODULE, PY_MODULE)
}

// ....