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Adding serious_python_web platform plugin
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‎src/serious_python_web/lib/serious_python_web.dart

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import 'dart:async';
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import 'dart:convert';
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import 'dart:html' as html;
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import 'dart:js_util' as js_util;
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import 'package:flutter/services.dart';
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import 'package:flutter_web_plugins/flutter_web_plugins.dart';
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import 'package:serious_python_platform_interface/serious_python_platform_interface.dart';
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import 'package:serious_python_web/pyodide.dart';
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class SeriousPythonWeb extends SeriousPythonPlatform {
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bool _isInitialized = false;
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PyodideInterface? _pyodide;
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final Set<String> _loadedModules = {};
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final String pyodideVersion = 'v0.27.2';
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late final String pyodideBaseURL = 'https://cdn.jsdelivr.net/pyodide/$pyodideVersion/full/';
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late final String pyodideJS = '${pyodideBaseURL}pyodide.js';
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/// Registers this class as the default instance of [SeriousPythonPlatform]
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static void registerWith(Registrar registrar) {
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SeriousPythonPlatform.instance = SeriousPythonWeb();
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}
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@override
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Future<String?> getPlatformVersion() async {
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return 'web';
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}
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Future<List<String>> _parseRequirementsFile(String requirementsFile) async {
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try {
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final content = await rootBundle.loadString(requirementsFile);
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return content
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.split('\n')
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.map((line) => line.trim())
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.where((line) =>
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line.isNotEmpty &&
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!line.startsWith('#') &&
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!line.startsWith('-'))
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.map((line) => line.split('==')[0].split('>=')[0].trim())
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.toList();
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} catch (e) {
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print('Error parsing requirements.txt: $e');
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rethrow;
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}
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}
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Future<String> _getRequirementsFileFromAssets() async {
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// Load the asset manifest
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// TODO Optimize not to load twice
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final manifestContent = await rootBundle.loadString('AssetManifest.json');
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final Map<String, dynamic> manifest = json.decode(manifestContent);
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// Filter for Python files in the specified directory
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return manifest.keys.firstWhere((String key) => key.contains("requirements.txt"));
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}
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Future<void> _loadPyodidePackages() async {
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try {
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// Parse requirements.txt
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final requirementsFile = await _getRequirementsFileFromAssets();
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final packages = await _parseRequirementsFile(requirementsFile);
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if (packages.isEmpty) {
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print("No packages found in requirements.txt");
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return;
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}
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print("Loading Pyodide packages: ${packages.join(', ')}");
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for(final package in packages) {
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// Load packages
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try {
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await js_util.promiseToFuture(
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js_util.callMethod(_pyodide!, 'loadPackage', [package])
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);
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} catch(e) {
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print('Could not import package: $package');
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}
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}
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print("Packages loaded successfully");
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} catch (e) {
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print('Error loading packages: $e');
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rethrow;
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}
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}
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Future<void> _initializePyodide() async {
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if (_pyodide != null) return;
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try {
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// Inject required meta tags first
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_injectMetaTags();
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// Create and add the script element
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final scriptElement = html.ScriptElement()
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..src = pyodideJS
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..type = 'text/javascript';
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html.document.head!.append(scriptElement);
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// Wait for script to load
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await _waitForPyodide();
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// Initialize Pyodide with correct base URL
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final config = js_util.jsify({
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'indexURL': pyodideBaseURL,
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'stdout': (String s) => print('Python stdout: $s'),
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'stderr': (String s) => print('Python stderr: $s')
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});
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final pyodidePromise = loadPyodide(config);
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_pyodide = await js_util.promiseToFuture<PyodideInterface>(pyodidePromise);
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// Test Python initialization
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await _runPythonCode("""
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import sys
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print(f"Python version: {sys.version}")
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""");
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print("Pyodide initialized successfully");
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} catch (e, stackTrace) {
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print('Error initializing Pyodide: $e');
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print('Stack trace: $stackTrace');
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rethrow;
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}
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}
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Future<void> _waitForPyodide() async {
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// TODO
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var attempts = 0;
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while (attempts < 100) {
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if (js_util.hasProperty(js_util.globalThis, 'loadPyodide')) {
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return;
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}
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await Future.delayed(const Duration(milliseconds: 100));
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attempts++;
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}
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throw Exception('Timeout waiting for Pyodide to load');
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}
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static void _injectMetaTags() {
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try {
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final head = html.document.head;
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// Check if meta tags already exist
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if (!head!.querySelectorAll('meta[name="cross-origin-opener-policy"]').isNotEmpty) {
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final coopMeta = html.MetaElement()
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..name = 'cross-origin-opener-policy'
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..content = 'same-origin';
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head.append(coopMeta);
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}
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if (!head.querySelectorAll('meta[name="cross-origin-embedder-policy"]').isNotEmpty) {
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final coepMeta = html.MetaElement()
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..name = 'cross-origin-embedder-policy'
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..content = 'require-corp';
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head.append(coepMeta);
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}
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} catch (e) {
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print('Error injecting meta tags: $e');
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}
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}
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Future<List<String>> _listPythonFilesInDirectory(String directory) async {
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// Load the asset manifest
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final manifestContent = await rootBundle.loadString('AssetManifest.json');
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final Map<String, dynamic> manifest = json.decode(manifestContent);
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// Filter for Python files in the specified directory
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return manifest.keys.where((String key) => key.contains(directory) && key.endsWith('.py')).toList();
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}
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Future<void> _loadModules(String moduleName, List<String> modulePaths) async {
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// Create a package directory in Pyodide's virtual filesystem
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await _runPythonCode('''
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import os
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import sys
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if not os.path.exists('/package'):
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os.makedirs('/package')
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if not os.path.exists('/package/$moduleName'):
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os.makedirs('/package/$moduleName')
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# Create __init__.py to make it a package
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with open(f'/package/$moduleName/__init__.py', 'w') as f:
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f.write('')
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if '/package' not in sys.path:
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sys.path.append('/package')
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''');
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for (final modulePath in modulePaths) {
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final moduleCode = await rootBundle.loadString(modulePath);
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final fileName = modulePath.split('/').last;
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// Use Pyodide's filesystem API to write module Code
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await _pyodide!.FS.writeFile('/package/$moduleName/$fileName', moduleCode, {'encoding': 'utf8'});
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}
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}
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Future<void> _loadModuleDirectories(List<String> modulePaths) async {
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final List<String> moduleNamesToImport = [];
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for(final directory in modulePaths) {
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final moduleName = directory.split("/").last;
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if(_loadedModules.contains(moduleName)) {
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continue;
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}
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final pythonFiles = await _listPythonFilesInDirectory(directory);
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await _loadModules(moduleName, pythonFiles);
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_loadedModules.add(moduleName);
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moduleNamesToImport.add(moduleName);
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}
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// Import the modules using pyimport
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for(final moduleNameToImport in moduleNamesToImport) {
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await _pyodide!.pyimport('$moduleNameToImport');
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}
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}
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Future<void> ensureInitialized(String appPath) async {
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if (!_isInitialized) {
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// TODO REQUIREMENTS FILE PATH: ARGUMENT?
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await _initializePyodide();
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await _loadPyodidePackages();
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_isInitialized = true;
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}
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}
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@override
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Future<String?> run(String appPath,
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{String? script, List<String>? modulePaths, Map<String, String>? environmentVariables, bool? sync}) async {
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print(environmentVariables);
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try {
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await ensureInitialized(appPath);
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// Load the Python code from the asset
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final pythonCode = await rootBundle.loadString(appPath);
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// Set environment variables if provided
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if (environmentVariables != null) {
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await _runPythonCode('''
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import os
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${environmentVariables.entries.map((e) => "os.environ['${e.key}'] = '${e.value}'").join('\n')}
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''');
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}
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// Add module paths if provided
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if (modulePaths != null) {
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int oldNModules = _loadedModules.length;
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await _loadModuleDirectories(modulePaths);
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int newNModules = _loadedModules.length;
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print("Loaded ${newNModules - oldNModules} new modules!");
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}
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final String debugCode = '''
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import os
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import sys
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print("Python version:", sys.version)
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print("Python path:", sys.path)
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print("Current working directory:", os.getcwd())
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print("Directory contents:", os.listdir('/package'))
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''';
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await _runPythonCode(debugCode + pythonCode);
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final result = _pyodide!.globals.get("pyodide_result");
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return result.toString();
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} catch (e) {
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print('Error running Python code: $e');
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return 'Error: $e';
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}
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}
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Future<void> _runPythonCode(String code) async {
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try {
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print("Running Python code: \n$code");
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final promise = _pyodide!.runPythonAsync(code);
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await js_util.promiseToFuture(promise);
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} catch (e) {
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print('Error running Python code: $e');
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rethrow;
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}
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}
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@override
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void terminate() {
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// No need to implement for web
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}
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}

‎src/serious_python_web/pubspec.yaml

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name: serious_python_web
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description: Web implementations of the serious_python plugin
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homepage: https://flet.dev
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repository: https://github.com/flet-dev/serious-python
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version: 0.8.7
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environment:
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sdk: '>=3.1.3 <4.0.0'
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flutter: '>=3.3.0'
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dependencies:
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flutter:
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sdk: flutter
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flutter_web_plugins:
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sdk: flutter
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js: ^0.6.7
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serious_python_platform_interface:
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path: ../serious_python_platform_interface
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dev_dependencies:
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flutter_test:
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sdk: flutter
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flutter_lints: ^2.0.0
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flutter:
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plugin:
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implements: serious_python
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platforms:
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web:
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pluginClass: SeriousPythonWeb
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fileName: serious_python_web.dart

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