How to import python package in flutter using Starflut?

Question

I'm building an app with Flutter and I need to use some Python code. For that I use the Starflut plugin (https://pub.dev/packages/starflut). I succeed to run the Python code, no issue here, but I want to import extra package.

To do so, I created a virtual environment where my app is located, then I downloaded by the pip installer numpy, cv2 and Pillow, still no issue there, the downloading went fine.

But, when I try to import numpy for example, my IDE (Visual Studio Code) tell me that there's an error :

Unable to import 'numpy' 

So here's my main.dart code (the only dart file, it's a test app):

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

import 'package:starflut/starflut.dart';

void main() => runApp(Main());

class Main extends StatefulWidget {
  @override
  _MainState createState() => _MainState();
}

class _MainState extends State<Main> {
  var _outputString = '';
  StarSrvGroupClass srvGroup;
  dynamic python;

  _MainState() {
    _initStarCore();
  }

  void showOutput(String info) async {
    if (info == null || info.length == 0) return;
    _outputString = info;
    setState(() {});
  }

  void _initStarCore() async {
    StarCoreFactory starcore = await Starflut.getFactory();
    StarServiceClass service =
        await starcore.initSimple("test", "123", 0, 0, []);
    String resPath = await Starflut.getResourcePath();
    await starcore.regMsgCallBackP(
        (int serviceGroupID, int uMsg, Object wParam, Object lParam) async {
      if (uMsg == Starflut.MSG_DISPMSG || uMsg == Starflut.MSG_DISPLUAMSG) {
        showOutput(wParam);
      }
      print("$serviceGroupID  $uMsg   $wParam   $lParam");
      return null;
    });
    srvGroup = await service["_ServiceGroup"];
    bool isAndroid = await Starflut.isAndroid();
    if (isAndroid == true) {
      String libraryDir = await Starflut.getNativeLibraryDir();
      String docPath = await Starflut.getDocumentPath();
      if (libraryDir.indexOf("arm64") > 0) {
        Starflut.unzipFromAssets("lib-dynload-arm64.zip", docPath, true);
      } else if (libraryDir.indexOf("x86_64") > 0) {
        Starflut.unzipFromAssets("lib-dynload-x86_64.zip", docPath, true);
      } else if (libraryDir.indexOf("arm") > 0) {
        Starflut.unzipFromAssets("lib-dynload-armeabi.zip", docPath, true);
      } else {
        //x86
        Starflut.unzipFromAssets("lib-dynload-x86.zip", docPath, true);
      }
      await Starflut.copyFileFromAssets("python3.6.zip",
          "flutter_assets/starfiles", null); //desRelatePath must be null
      await Starflut.copyFileFromAssets(
          "program.py", "flutter_assets/starfiles", "flutter_assets/starfiles");
    }
    if (await srvGroup.initRaw("python36", service) == true) {
      _outputString = "init starcore and python 3.6 successfully";
    } else {
      _outputString = "init starcore and python 3.6 failed";
    }

    await srvGroup.loadRawModule("python", "",
        resPath + "/flutter_assets/starfiles/" + "program.py", false);
    python = await service.importRawContext("python", "", false, "");

    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      //_counter++;
    });
  }

  void runScriptCode() async {
    var result = await python.call("multiply", [5, 2]);
    _outputString = result.toString();

    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: FlatButton(
            color: Colors.red,
            child: Text(_outputString),
            onPressed: () {
              runScriptCode();
            },
          ),
        ),
      ),
    );
  }
}

and my Python file:

import numpy as np # (to test)

def multiply(a, b):
    return a*b

Here's my tree structure if it can help: The tree structure of my Flutter project

Hopping you can help me.

Thanks in advance !

Solution

You can use chaquopy plugin for flutter, if you want to integrate python packages inside your android app.

Comments

[Vayhuit]

I already tried it with flask, and it worked pretty well but, I don't need to pay a domain name or something if I want to deploy my app ? Or even though I deploy it, Can I steel use a local server ? And a little last question, the library import is more easy if I use this way ? Thanks for your answer !

[bitinerant]

Note that using Chaquo requires a license, though it says that license is free for open-source apps. They also have a "Python SDK for Android" on GitHub but I think it's just a demo project. I don't think Chaquopy itself is open-source.

[Jay Dangar]

yes it's not but if you are creating open source app, then you can contact Chaquopy creator and you'll get free license to use.