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Javascript – Electron JS: spawn() works fine with "python –version" but with "python" I don't get any output

I’m using Electron JS and trying to execute a command in a child process using spawn() from the child_process module.

When I run the command python --version, it correctly outputs the version of Python in the child process. However, when I run just python, the process seems to start but doesn’t output anything, and the behavior appears inconsistent.

Here is a simplified version of my code:

const { spawn } = require('child_process');



const child = spawn('python', [], { shell: true });



child.stdout.on('data', (data) => {

  console.log(`stdout: ${data}`);

});



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

  console.error(`stderr: ${data}`);

});



child.on('close', (code) => {

  console.log(`Child process exited with code ${code}`);

});

What I expect:

Running python should launch the interactive Python REPL and provide output.

What actually happens:

When I run python --version, it works fine.

When I run just python, there is no output or REPL interaction visible in my app.

Additional Details:

Electron version: v34.0.0

Node.js version: v23.6.0

IDE: Visual Studio Code

OS: Windows 11 24H2

What could be causing this issue? Do I need to set up the child process differently to handle REPL or interactive commands in Electron?

Tags:

2

Answers


  1. 0

    To manage interactivity (arrow keys, etc) Python requires more than a connected stdout, it requires a pseudo-terminal. Otherwise it’ll just quit because you didn’t give it any instructions and without a terminal it can’t request any. You can simulate what your code is doing like this:

    python3 </dev/null | /bin/cat

    And as you can see, nothing happens.

    If you want to link the repl to a web UI then you’ll need a fairly complex setup out of scope for this answer, but search for web terminal emulators and pseudo-terminals in node. If you just want to run some python, pipe it into stdin and then close it. Python will execute the result.

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  2. 0

    Your code is indeed correct, the only thing you’ve missed is that running a Python process as a spawn with no arguments will make it search arguments for a script file. To force interactive mode, you should add -i to the argument list (note that on a regular terminal it works fine without this).
    This NodeJS code snippet seems to solve your problem:

    const { spawn } = require("child_process");

const py = spawn("python", ["-i"]);

py.on("close", code => console.log("Closed: " + code));

py.stdout.on("data", data => {
    console.log(data.toString());
})

py.stderr.on("data", data => {
    console.log(data.toString());
})

// Some example commands
const commands = [
    "2 + 2",
    "print('Test')",
    "print(3 + 2)",
    "5 - 8",
    "exit(1234)"
]

var i = 0;
var input = setInterval(function() {
    py.stdin.write(commands[i] + 'n');
    i++;
    if (i >= commands.length) clearInterval(input);
}, 500);
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