Bundling Python inside an Electron app#

In development mode#

In my Electron app’s root folder I ran the following:

1
wget https://github.com/indygreg/python-build-standalone/releases/download/20210724/cpython-3.9.6-x86_64-apple-darwin-install_only-20210724T1424.tar.gz
2
tar -xzvf cpython-3.9.6-x86_64-apple-darwin-install_only-20210724T1424.tar.gz

This gave me a python/ subfolder containing a full standalone Python, ready to run on my Mac.

Running python/bin/python3.9 --version confirms that this is working correctly.

Calling Python from Electron#

I used the Node.js child_process.execFile() function to execute Python scripts from inside Electron, like this:

1
const cp = require("child_process");
2
const util = require("util");
3
const execFile = util.promisify(cp.execFile);
4

5
await execFile(path_to_python, ["-m", "random"]);

path_to_python needs to be the path to that python3.9 executable. I wrote a findPython() function to find that, like so:

1
const fs = require("fs");
2

3
function findPython() {
4
  const possibilities = [
5
    // In packaged app
6
    path.join(process.resourcesPath, "python", "bin", "python3.9"),
7
    // In development
8
    path.join(__dirname, "python", "bin", "python3.9"),
9
  ];
10
  for (const path of possibilities) {
11
    if (fs.existsSync(path)) {
12
      return path;
13
    }
14
  }
15
  console.log("Could not find python3, checked", possibilities);
16
  app.quit();
17
}

The resourcesPath bit here works for the packaged and deployed application.

Packaging the app#

I needed that python folder to be bundled up as part of the Datasette.app application bundle. I achieved that by adding the following to my "build" section in package.json:

1
    "extraResources": [
2
      {
3
        "from": "python",
4
        "to": "python",
5
        "filter": [
6
          "**/*"
7
        ]
8
      }
9
    ]

This causes electron-builder to copy the contents of that python folder into Datasette.app/Contents/Resources/python in the packaged application.

My findPython() function earlier knows to look for it there by creating a path to it starting with process.resourcesPath.

Signing and notarizing#

I wrote extensive notes on signing and notarizing in Signing and notarizing an Electron app for distribution using GitHub Actions, which includes details on how I signed the Python binaries that ended up included in the package due to this pattern.