如何在 NodeJS 中使用 Spawn 将数据从子进程发送回父进程

Question

我正在尝试使用 spawn 子进程从 NodeJS 运行 python 脚本。 我能够成功地让 python 运行并使用控制台日志查看数据，但无法将实际数据发送回父函数以便我可以在其他地方使用它。

这是在 Node.js 中调用 spawn 的“Child.js”文件：

//Child.js:  Node.js file that executes a python script using spawn...

function run_python_script(jsonString, callback){

    //spawn new child process to call the python script
    const {spawn} = require('child_process');
    const python = spawn('python3', ["-c",`from apps import python_app; python_app.run(${jsonString});`]);

    var dataToSend = ''
    python.stdout.on('data', (data) => {
        dataToSend = data.toString() //<---How do I return this back to other functions?
        return callback(dataToSend)  //<---this is not returning back to other functions.
    })

    python.stderr.on('data', (data)=>{
            console.log(`stderr: ${data}`)
        })
    }

module.exports = { run_python_script };

================================================ ===================这是调用上面我想从 Python 接收数据的“Child.js”文件的文件...

const Child = require('./Child.js');

const callback = (x)=>{return x} //<--simply returns what's put in

let company_data = {
    "industry": "Financial Services",
    "revenue": 123456789
}
jsonString = JSON.stringify(company_data);

let result = ''
result = Child.run_python_script(jsonString, callback) //<-- I want the results from python to be stored here so I can use it elsewhere. 

console.log(result) //<--this returns "undefined".  Data isn't coming back

Answer 1

如果不需要异步生成 Python 进程，则可以使用spawnSync而不是spawn来直接获取包含其stdout和stderr作为字符串的对象：

const { spawnSync } = require('child_process');
const python = spawnSync('python3', ['-c', `print("hello"); assert False`], { encoding: "utf8" });

// Access stdout
console.log(python.stdout)

// Access stderr
console.log(python.stderr)

Answer 2

我想通了。 我将整个 spawn 例程包装在 Promise 中

// child.js

function run_python_script(jsonString){

    const promise = new Promise((resolve, reject) => {
    
        // spawn new child process to call the python script
        const {spawn} = require('child_process');
    
        const python = spawn('python3', ["-c",`from apps import python_app; python_app.run(${jsonString});`])

        var dataToSend = ''
        python.stdout.on('data', (data) => {
            dataToSend = data.toString()
        })

        python.stderr.on('data', (data)=>{
            console.log(`stderr: ${data}`)
            reject(new Error(`stderr occured`))
        })

        python.on('close', (code)=>{
            if (code !=0){
                reject(new Error(`error code: ${code}`))
            }else{
                resolve(dataToSend)
            }
        })
    })

    return promise
}

module.exports = { run_python_script };

================================================ ==========================这里是调用上面子函数的父函数：

//Parent.js

const Child = require('./Child.js');

var data = {
    "industry": "Financial Services",
    "revenue": 12345678
}

var jsonString = JSON.stringify(data);

var result = ''
Child.run_python_script(jsonString).then(returnedData => {
    var result = returnedData;
    console.log(result)
})
.catch(err => {
    console.log(err)
})