Node.js communicate with python-shell

Question

I have the json data in nodejs. And I try to pass this data to python. But I can't get a reply from PythonFIle.

jsonData Format

[
 {
 id: 123,
 option: ["A","B"],
 description: "Why I can't pass this data to Python" 
 },
 {
 id: 456,
 option: ["A","B"],
 description: "Why I can't pass this data to Python" 
 },{....}
]

node.js

var { PythonShell } = require('python-shell'); 
let pyshell = new PythonShell('../pythonFile.py', { mode: 'json ' }); 
pyshell.send(jsonData)
pyshell.on('message', function (message) { //But never receive data from pythonFile.
 console.log("HIHI, I am pythonFile context") //Not appear this message
 console.log(message); //Not appear this message
 });
pyshell.end(function (err) { // Just run it
 if (err) throw err;
 console.log('finished'); //appear this message
 });

pythonFile.py

import json
import sys
jsJSONdata = input() //recieve js data
print(jsJSONdata) //send jsJSONdata to nodejs

Thanks for your help.

Answer 1

First of all, you can not send a JSON variable by send() method, because this method sends to stdin which accepts only string and bytes. Please try to execute my example:

test.py

value = input()
print(f"Python script response: {value}")

test.js

const {PythonShell} = require('python-shell')
const pyshell = new PythonShell('test.py');
pyshell.send(JSON.stringify({"hello": "hello"}));
pyshell.on('message', function (message) {
 console.log(message);
});
pyshell.end(function (err,code,signal) {
 if (err) throw err;
 console.log('finished');
});

If this example works for you, then change {"hello": "hello"} to jsonData.

I hope that I helped you.

• Creek: Thank you. It can run. But I have a question about the Python-shell API said Sends a message to the Python script via stdin. The data is formatted according to the selected mode (text or JSON), or through a custom function when formatter is specified.. So really can't send JSON ..? Sorry about my question. But I really want to know.
• Nazarii Kulyk: You can send JSON by only like a string, because if you send JSON variable without JSON.stringify(), your python scripts will accept [object Object]. But I think that it is no problem because you can use a json library for python (docs.python.org/3/library/json.html) and covert accepted string to JSON or from JSON to string. And you can convert the accepted string variable in your js event with function JSON.parse().