问题:如何从Node.js调用Python函数

我有一个Express Node.js应用程序,但我还有一个机器学习算法可在Python中使用。有没有一种方法可以从Node.js应用程序调用Python函数来利用机器学习库的功能?

I have an Express Node.js application, but I also have a machine learning algorithm to use in Python. Is there a way I can call Python functions from my Node.js application to make use of the power of machine learning libraries?


回答 0

我知道的最简单的方法是使用与节点打包在一起的“ child_process”包。

然后,您可以执行以下操作:

const spawn = require("child_process").spawn;
const pythonProcess = spawn('python',["path/to/script.py", arg1, arg2, ...]);

然后,所有要做的就是确保您import sys在python脚本中,然后可以arg1使用 sys.argv[1]arg2使用 sys.argv[2],等等进行访问。

要将数据发送回节点,只需在python脚本中执行以下操作:

print(dataToSendBack)
sys.stdout.flush()

然后节点可以使用以下方法侦听数据:

pythonProcess.stdout.on('data', (data) => {
    // Do something with the data returned from python script
});

由于这允许使用spawn将多个参数传递给脚本,因此您可以重组python脚本,以便其中一个参数决定调用哪个函数,而另一个参数传递给该函数,依此类推。

希望这很清楚。让我知道是否需要澄清。

Easiest way I know of is to use “child_process” package which comes packaged with node.

Then you can do something like:

const spawn = require("child_process").spawn;
const pythonProcess = spawn('python',["path/to/script.py", arg1, arg2, ...]);

Then all you have to do is make sure that you import sys in your python script, and then you can access arg1 using sys.argv[1], arg2 using sys.argv[2], and so on.

To send data back to node just do the following in the python script:

print(dataToSendBack)
sys.stdout.flush()

And then node can listen for data using:

pythonProcess.stdout.on('data', (data) => {
    // Do something with the data returned from python script
});

Since this allows multiple arguments to be passed to a script using spawn, you can restructure a python script so that one of the arguments decides which function to call, and the other argument gets passed to that function, etc.

Hope this was clear. Let me know if something needs clarification.


回答 1

来自Python背景并希望将其机器学习模型集成到Node.js应用程序中的人员的:

它使用child_process核心模块:

const express = require('express')
const app = express()

app.get('/', (req, res) => {

    const { spawn } = require('child_process');
    const pyProg = spawn('python', ['./../pypy.py']);

    pyProg.stdout.on('data', function(data) {

        console.log(data.toString());
        res.write(data);
        res.end('end');
    });
})

app.listen(4000, () => console.log('Application listening on port 4000!'))

不需要 sys在您的Python脚本中模块。

以下是使用以下命令执行任务的更模块化的方式Promise

const express = require('express')
const app = express()

let runPy = new Promise(function(success, nosuccess) {

    const { spawn } = require('child_process');
    const pyprog = spawn('python', ['./../pypy.py']);

    pyprog.stdout.on('data', function(data) {

        success(data);
    });

    pyprog.stderr.on('data', (data) => {

        nosuccess(data);
    });
});

app.get('/', (req, res) => {

    res.write('welcome\n');

    runPy.then(function(fromRunpy) {
        console.log(fromRunpy.toString());
        res.end(fromRunpy);
    });
})

app.listen(4000, () => console.log('Application listening on port 4000!'))

Example for people who are from Python background and want to integrate their machine learning model in the Node.js application:

It uses the child_process core module:

const express = require('express')
const app = express()

app.get('/', (req, res) => {

    const { spawn } = require('child_process');
    const pyProg = spawn('python', ['./../pypy.py']);

    pyProg.stdout.on('data', function(data) {

        console.log(data.toString());
        res.write(data);
        res.end('end');
    });
})

app.listen(4000, () => console.log('Application listening on port 4000!'))

It doesn’t require sys module in your Python script.

Below is a more modular way of performing the task using Promise:

const express = require('express')
const app = express()

let runPy = new Promise(function(success, nosuccess) {

    const { spawn } = require('child_process');
    const pyprog = spawn('python', ['./../pypy.py']);

    pyprog.stdout.on('data', function(data) {

        success(data);
    });

    pyprog.stderr.on('data', (data) => {

        nosuccess(data);
    });
});

app.get('/', (req, res) => {

    res.write('welcome\n');

    runPy.then(function(fromRunpy) {
        console.log(fromRunpy.toString());
        res.end(fromRunpy);
    });
})

app.listen(4000, () => console.log('Application listening on port 4000!'))

回答 2

python-shell模块extrabacon是通过Node.js运行Python脚本的一种简单方法,它具有基本但有效的进程间通信和更好的错误处理能力。

安装: npm install python-shell

运行一个简单的Python脚本:

var PythonShell = require('python-shell');

PythonShell.run('my_script.py', function (err) {
  if (err) throw err;
  console.log('finished');
});

使用参数和选项运行Python脚本:

var PythonShell = require('python-shell');

var options = {
  mode: 'text',
  pythonPath: 'path/to/python',
  pythonOptions: ['-u'],
  scriptPath: 'path/to/my/scripts',
  args: ['value1', 'value2', 'value3']
};

PythonShell.run('my_script.py', options, function (err, results) {
  if (err) 
    throw err;
  // Results is an array consisting of messages collected during execution
  console.log('results: %j', results);
});

有关完整的文档和源代码,请查看https://github.com/extrabacon/python-shell

The python-shell module by extrabacon is a simple way to run Python scripts from Node.js with basic, but efficient inter-process communication and better error handling.

Installation: npm install python-shell.

Running a simple Python script:

var PythonShell = require('python-shell');

PythonShell.run('my_script.py', function (err) {
  if (err) throw err;
  console.log('finished');
});

Running a Python script with arguments and options:

var PythonShell = require('python-shell');

var options = {
  mode: 'text',
  pythonPath: 'path/to/python',
  pythonOptions: ['-u'],
  scriptPath: 'path/to/my/scripts',
  args: ['value1', 'value2', 'value3']
};

PythonShell.run('my_script.py', options, function (err, results) {
  if (err) 
    throw err;
  // Results is an array consisting of messages collected during execution
  console.log('results: %j', results);
});

For the full documentation and source code, check out https://github.com/extrabacon/python-shell


回答 3

现在,您可以使用支持Python和Javascript的RPC库,例如zerorpc

从他们的首页:

Node.js客户端

var zerorpc = require("zerorpc");

var client = new zerorpc.Client();
client.connect("tcp://127.0.0.1:4242");

client.invoke("hello", "RPC", function(error, res, more) {
    console.log(res);
});

Python服务器

import zerorpc

class HelloRPC(object):
    def hello(self, name):
        return "Hello, %s" % name

s = zerorpc.Server(HelloRPC())
s.bind("tcp://0.0.0.0:4242")
s.run()

You can now use RPC libraries that support Python and Javascript such as zerorpc

From their front page:

Node.js Client

var zerorpc = require("zerorpc");

var client = new zerorpc.Client();
client.connect("tcp://127.0.0.1:4242");

client.invoke("hello", "RPC", function(error, res, more) {
    console.log(res);
});

Python Server

import zerorpc

class HelloRPC(object):
    def hello(self, name):
        return "Hello, %s" % name

s = zerorpc.Server(HelloRPC())
s.bind("tcp://0.0.0.0:4242")
s.run()

回答 4

先前的大多数答案都将on(“ data”)中的promise称为成功,这不是正确的方法,因为如果您收到大量数据,您只会得到第一部分。相反,您必须在结束事件上执行此操作。

const { spawn } = require('child_process');
const pythonDir = (__dirname + "/../pythonCode/"); // Path of python script folder
const python = pythonDir + "pythonEnv/bin/python"; // Path of the Python interpreter

/** remove warning that you don't care about */
function cleanWarning(error) {
    return error.replace(/Detector is not able to detect the language reliably.\n/g,"");
}

function callPython(scriptName, args) {
    return new Promise(function(success, reject) {
        const script = pythonDir + scriptName;
        const pyArgs = [script, JSON.stringify(args) ]
        const pyprog = spawn(python, pyArgs );
        let result = "";
        let resultError = "";
        pyprog.stdout.on('data', function(data) {
            result += data.toString();
        });

        pyprog.stderr.on('data', (data) => {
            resultError += cleanWarning(data.toString());
        });

        pyprog.stdout.on("end", function(){
            if(resultError == "") {
                success(JSON.parse(result));
            }else{
                console.error(`Python error, you can reproduce the error with: \n${python} ${script} ${pyArgs.join(" ")}`);
                const error = new Error(resultError);
                console.error(error);
                reject(resultError);
            }
        })
   });
}
module.exports.callPython = callPython;

呼叫:

const pythonCaller = require("../core/pythonCaller");
const result = await pythonCaller.callPython("preprocessorSentiment.py", {"thekeyYouwant": value});

Python:

try:
    argu = json.loads(sys.argv[1])
except:
    raise Exception("error while loading argument")

Most of previous answers call the success of the promise in the on(“data”), it is not the proper way to do it because if you receive a lot of data you will only get the first part. Instead you have to do it on the end event.

const { spawn } = require('child_process');
const pythonDir = (__dirname + "/../pythonCode/"); // Path of python script folder
const python = pythonDir + "pythonEnv/bin/python"; // Path of the Python interpreter

/** remove warning that you don't care about */
function cleanWarning(error) {
    return error.replace(/Detector is not able to detect the language reliably.\n/g,"");
}

function callPython(scriptName, args) {
    return new Promise(function(success, reject) {
        const script = pythonDir + scriptName;
        const pyArgs = [script, JSON.stringify(args) ]
        const pyprog = spawn(python, pyArgs );
        let result = "";
        let resultError = "";
        pyprog.stdout.on('data', function(data) {
            result += data.toString();
        });

        pyprog.stderr.on('data', (data) => {
            resultError += cleanWarning(data.toString());
        });

        pyprog.stdout.on("end", function(){
            if(resultError == "") {
                success(JSON.parse(result));
            }else{
                console.error(`Python error, you can reproduce the error with: \n${python} ${script} ${pyArgs.join(" ")}`);
                const error = new Error(resultError);
                console.error(error);
                reject(resultError);
            }
        })
   });
}
module.exports.callPython = callPython;

Call:

const pythonCaller = require("../core/pythonCaller");
const result = await pythonCaller.callPython("preprocessorSentiment.py", {"thekeyYouwant": value});

python:

try:
    argu = json.loads(sys.argv[1])
except:
    raise Exception("error while loading argument")

回答 5

我在节点10和子进程上1.0.2。来自python的数据是一个字节数组,必须进行转换。这是在python中发出http请求的另一个快速示例。

节点

const process = spawn("python", ["services/request.py", "https://www.google.com"])

return new Promise((resolve, reject) =>{
    process.stdout.on("data", data =>{
        resolve(data.toString()); // <------------ by default converts to utf-8
    })
    process.stderr.on("data", reject)
})

request.py

import urllib.request
import sys

def karl_morrison_is_a_pedant():   
    response = urllib.request.urlopen(sys.argv[1])
    html = response.read()
    print(html)
    sys.stdout.flush()

karl_morrison_is_a_pedant()

ps不是一个人为的例子,因为节点的http模块不会加载我需要发出的一些请求

I’m on node 10 and child process 1.0.2. The data from python is a byte array and has to be converted. Just another quick example of making a http request in python.

node

const process = spawn("python", ["services/request.py", "https://www.google.com"])

return new Promise((resolve, reject) =>{
    process.stdout.on("data", data =>{
        resolve(data.toString()); // <------------ by default converts to utf-8
    })
    process.stderr.on("data", reject)
})

request.py

import urllib.request
import sys

def karl_morrison_is_a_pedant():   
    response = urllib.request.urlopen(sys.argv[1])
    html = response.read()
    print(html)
    sys.stdout.flush()

karl_morrison_is_a_pedant()

p.s. not a contrived example since node’s http module doesn’t load a few requests I need to make


回答 6

您可以将自己的python进行转换,然后像调用JavaScript一样对其进行调用。我已经成功完成了此步骤,甚至还可以在浏览器中运行la brython

You could take your python, transpile it, and then call it as if it were javascript. I have done this succesfully for screeps and even got it to run in the browser a la brython.


回答 7

/*eslint-env es6*/
/*global require*/
/*global console*/
var express = require('express'); 
var app = express();

// Creates a server which runs on port 3000 and  
// can be accessed through localhost:3000
app.listen(3000, function() { 
    console.log('server running on port 3000'); 
} ) 

app.get('/name', function(req, res) {

    console.log('Running');

    // Use child_process.spawn method from  
    // child_process module and assign it 
    // to variable spawn 
    var spawn = require("child_process").spawn;   
    // Parameters passed in spawn - 
    // 1. type_of_script 
    // 2. list containing Path of the script 
    //    and arguments for the script  

    // E.g : http://localhost:3000/name?firstname=Levente
    var process = spawn('python',['apiTest.py', 
                        req.query.firstname]);

    // Takes stdout data from script which executed 
    // with arguments and send this data to res object
    var output = '';
    process.stdout.on('data', function(data) {

        console.log("Sending Info")
        res.end(data.toString('utf8'));
    });

    console.log(output);
}); 

这对我有用。您的python.exe必须添加到此代码段的路径变量中。另外,请确保您的python脚本位于项目文件夹中。

/*eslint-env es6*/
/*global require*/
/*global console*/
var express = require('express'); 
var app = express();

// Creates a server which runs on port 3000 and  
// can be accessed through localhost:3000
app.listen(3000, function() { 
    console.log('server running on port 3000'); 
} ) 

app.get('/name', function(req, res) {

    console.log('Running');

    // Use child_process.spawn method from  
    // child_process module and assign it 
    // to variable spawn 
    var spawn = require("child_process").spawn;   
    // Parameters passed in spawn - 
    // 1. type_of_script 
    // 2. list containing Path of the script 
    //    and arguments for the script  

    // E.g : http://localhost:3000/name?firstname=Levente
    var process = spawn('python',['apiTest.py', 
                        req.query.firstname]);

    // Takes stdout data from script which executed 
    // with arguments and send this data to res object
    var output = '';
    process.stdout.on('data', function(data) {

        console.log("Sending Info")
        res.end(data.toString('utf8'));
    });

    console.log(output);
}); 

This worked for me. Your python.exe must be added to you path variables for this code snippet. Also, make sure your python script is in your project folder.


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