pocketpy/plugins/flutter

Introduction

This plugin provides object-oriented interfaces including full functionality of PocketPy C-API.

Run the following script to install this plugin.

flutter pub add pocketpy

Requirements

For Android

You may need to set the Android NDK version to "21.4.7075529" or higher in android/app/build.gradle.

android {
    ndkVersion "21.4.7075529"
}

For iOS

It should work without any setup.

For Web

Download an artifact from https://github.com/blueloveTH/pocketpy/releases/latest.

Unzip it and copy web/lib into your root folder where index.html locates.

...
lib/pocketpy.js
lib/pocketpy.wasm
index.html
...

Then open index.html and add this line before flutter.js tag.

...
  <!-- This script initializes WASM of pocketpy -->
  <script src="./lib/pocketpy.js"></script>

  <!-- This script adds the flutter initialization JS code -->
  <script src="flutter.js" defer></script>
...

For Windows

VS2017 or higher is required to build the windows .dll. Make sure you have C++ component installed.

Basic Example

import 'package:pocketpy/pocketpy.dart' as pkpy;

// Create a virtual machine
pkpy.VM vm = pkpy.VM();

// Run a script
String code = 'print("Hello World!")';
vm.exec(code);

// Read the output
var _o = vm.read_output();
print(_o.stdout)	// "Hello world!\n"
print(_o.stderr)	// ""
    
// Create a binding
vm.bind<int>("builtins", "add", (int x, int y) => x + y);
vm.eval("add(1, 2)");	// '3'

REPL Widget Example

import 'dart:io';

import 'package:flutter/material.dart';
import 'package:pocketpy/pocketpy.dart' as pkpy;

void main() {
  runApp(const MaterialApp(home: MyApp()));
}

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  late final pkpy.VM vm;
  late final pkpy.REPL repl;
  bool needMoreLines = false;

  final TextEditingController _controller = TextEditingController();
  final StringBuffer buffer = StringBuffer();

  @override
  void initState() {
    super.initState();

    // create a pocketpy virtual machine
    vm = pkpy.VM();

    // create a REPL
    repl = pkpy.REPL(vm);

    WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
      refresh();
    });
  }

  void addMessage(String text) {
    setState(() {
      buffer.write(text);
    });
  }

  void submitCode() {
    var text = _controller.text;
    _controller.clear();
    setState(() {
      buffer.write(needMoreLines ? '... $text' : '>>> $text\n');
    });

    needMoreLines = repl.input(text);
    refresh();
  }

  void refresh() {
    // ignore: no_leading_underscores_for_local_identifiers
    var _o = vm.read_output();
    if (_o.stdout.isNotEmpty) buffer.write(_o.stdout);
    if (_o.stderr.isNotEmpty) buffer.write(_o.stderr);
    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    var style = const TextStyle(fontSize: 16);
    return Scaffold(
      appBar: AppBar(
        title: const Text('Demo'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Column(crossAxisAlignment: CrossAxisAlignment.start, children: [
          Expanded(
            child: SingleChildScrollView(
              reverse: true,
              child: Text(
                buffer.toString(),
                style: style,
                textAlign: TextAlign.left,
              ),
            ),
          ),
          const SizedBox(
            height: 16,
          ),
          SizedBox(
            height: 50,
            child: TextFormField(
              controller: _controller,
              style: style,
              maxLines: 1,
              decoration: const InputDecoration(
                border: OutlineInputBorder(),
                hintText: 'Enter Python code',
              ),
            ),
          ),
          Container(
            height: 60,
            alignment: Alignment.centerRight,
            child: MaterialButton(
                onPressed: submitCode,
                color: Colors.blue,
                textColor: Colors.white,
                child: const Text('Run')),
          ),
        ]),
      ),
    );
  }
}

basic

The following table shows the basic features of pkpy with respect to cpython. The features marked with YES are supported, and the features marked with NO are not supported.

Name	Example	Supported
If Else	if..else..elif	YES
Loop	for/while/break/continue	YES
Function	def f(x,*args,y=1):	YES
Subclass	class A(B):	YES
List	[1, 2, 'a']	YES
ListComp	[i for i in range(5)]	YES
Slice	a[1:2], a[:2], a[1:]	YES
Tuple	(1, 2, 'a')	YES
Dict	{'a': 1, 'b': 2}	YES
F-String	f'value is {x}'	YES
Unpacking	a, b = 1, 2	YES
Star Unpacking	a, *b = [1, 2, 3]	YES
Exception	raise/try..catch	YES
Dynamic Code	eval()/exec()	YES
Reflection	hasattr()/getattr()/setattr()	YES
Import	import/from..import	YES
Context Block	with <expr> as <id>:	YES
Type Annotation	def f(a:int, b:float=1)	YES
Generator	yield i	YES
Decorator	@cache	YES