Preliminary python support

package.json

@@ -8,6 +8,7 @@
   },
   "homepage": "https://rameshvarun.github.io/blog-cells/",
   "devDependencies": {
+    "@codemirror/lang-python": "^6.1.3",
     "@types/jest": "^29.5.4",
     "@types/react": "^18.2.20",
     "@types/react-dom": "^18.2.7",

src/blog-cells.tsx

@@ -13,13 +13,19 @@ const editors: any[] = [];
 const events = new EventTarget();
 
 import { JavaScriptKernel } from "./javascript-kernel";
-const kernel = new JavaScriptKernel();
+import { PythonKernel } from "./python-kernel";
+import { Kernel } from "./kernel";
+
+const KERNELS: Map<string, Kernel> = new Map();
+KERNELS.set("javascript", new JavaScriptKernel());
+KERNELS.set("python", new PythonKernel());
 
 class Cell extends React.Component<
   {
     code: string;
     autoRun: boolean;
     hideable: boolean;
+    kernel: Kernel;
     onMount?: () => void;
   },
   any
@@ -129,7 +135,7 @@ class Cell extends React.Component<
       extensions: [
         history(),
         lineNumbers(),
-        kernel.getSyntaxHighlighter(),
+        this.props.kernel.getSyntaxHighlighter(),
         oneDark,
         keymap.of([...defaultKeymap, ...historyKeymap]),
       ],
@@ -160,7 +166,7 @@ class Cell extends React.Component<
       setTimeout(() => resolve(), 500);
     });
 
-    kernel.run(
+    this.props.kernel.run(
       code,
       (line) => {
         this.setState((state) => {
@@ -196,6 +202,10 @@ domLoaded.then(() => {
 
   for (const script of scripts) {
     const code = script.textContent?.trim() || "";
+
+    const kernelName = script.dataset.kernel || "javascript";
+    const kernel = KERNELS.get(kernelName)!;
+
     const autoRun = script.dataset.autorun === "true";
     const hidden = script.dataset.hidden === "true";
 
@@ -208,6 +218,7 @@ domLoaded.then(() => {
         code={code}
         autoRun={autoRun}
         hideable={hidden}
+        kernel={kernel}
         onMount={() => {
           // Remove the script tag once the cell succesfully mounts.
           script.remove();

src/index.html

@@ -94,6 +94,10 @@ <h1><a href="https://github.com/rameshvarun/blog-cells">blog-cells</a> demo</h1>
 console.assert(3 == 4, "3 does not equal 4.");
 </script>
 
+<p>You can use other languages like Python.</p>
+<script type="text/notebook-cell" data-autorun="true" data-kernel="python">print("Hello World from Python!")
+</script>
+
 <link rel="stylesheet" href="./blog-cells.css" />
 <script type="module" src="./blog-cells.js"></script>
 

src/javascript-kernel/index.ts

@@ -6,14 +6,9 @@ import { javascript } from "@codemirror/lang-javascript";
 import { Kernel, OutputLine } from "../kernel";
 import { ExecutionRequest, ExecutionResponse } from "./types";
 
-export class JavaScriptKernel implements Kernel {
+export class JavaScriptKernel extends Kernel {
     worker: Worker = new Worker(URL.createObjectURL(blob));
 
-    requestID: number = 0;
-    getRequestID() {
-        return this.requestID++;
-    }
-
     run(code: string, onOutput: (line: OutputLine) => void, onDone: () => void) {
         // Generate a unique ID to track this execution request.
         const requestID = this.getRequestID();

src/kernel.ts

@@ -1,11 +1,16 @@
 import { LanguageSupport } from "@codemirror/language";
 
 export type OutputLine = {
-  type: string;
+  type: 'log' | 'error' | 'warn';
   line: string;
 };
 
-export interface Kernel {
-  run(code: string, onOutput: (line: OutputLine) => void, onDone: () => void);
-  getSyntaxHighlighter(): LanguageSupport;
+export abstract class Kernel {
+  requestID: number = 0;
+  getRequestID() {
+      return this.requestID++;
+  }
+
+  abstract run(code: string, onOutput: (line: OutputLine) => void, onDone: () => void);
+  abstract getSyntaxHighlighter(): LanguageSupport;
 }

src/python-kernel/index.ts

@@ -0,0 +1,40 @@
+// @ts-ignore - Load worker source code.
+import WORKER_SRC from "!raw-loader!ts-loader!./worker.ts";
+const blob = new Blob([WORKER_SRC], { type: "application/javascript" });
+
+import { python } from "@codemirror/lang-python";
+import { Kernel, OutputLine } from "../kernel";
+
+export class PythonKernel extends Kernel {
+    worker: Worker = new Worker(URL.createObjectURL(blob));
+
+    run(code: string, onOutput: (line: OutputLine) => void, onDone: () => void) {
+        // Generate a unique ID to track this execution request.
+        const requestID = this.getRequestID();
+
+        const messageHandler = (e: MessageEvent) => {
+            if (e.data.requestID != requestID) return;
+
+            if (e.data.kind === "run-code-output") {
+                onOutput(e.data.output);
+            } else if (e.data.kind === "run-code-done") {
+                this.worker.removeEventListener("message", messageHandler);
+                onDone();
+            }
+        };
+
+        this.worker.addEventListener("message", messageHandler);
+
+        // Post the code to the worker.
+        this.worker.postMessage({
+            kind: "run-code",
+            code: code,
+            requestID: requestID,
+        });
+    }
+
+
+    getSyntaxHighlighter() {
+        return python();
+    }
+}

src/python-kernel/worker.ts

@@ -0,0 +1,52 @@
+importScripts("https://cdn.jsdelivr.net/npm/pyodide@0.23.2/pyodide.min.js");
+declare var loadPyodide;
+
+let onStdout: ((str) => void) | null = null;
+
+// Start loading Pyodide asynchronously.
+const loadPython = (async () => {
+  return await loadPyodide({
+    stdout: (msg) => {
+      if (msg === "Python initialization complete") return;
+      if (onStdout) onStdout(msg);
+    },
+  });
+})();
+
+self.onmessage = async (e: MessageEvent) => {
+  console.log("Worker received message: %o", e);
+  const requestID = e.data.requestID;
+
+  if (e.data.kind === "run-code") {
+    // Register stdout callback.
+    onStdout = (msg) => {
+      self.postMessage({
+        kind: "run-code-output",
+        requestID: requestID,
+        output: {type: "log", line: msg},
+      });
+    };
+
+    try {
+      // Wait for Pyodide to load.
+      const pyodide = await loadPython;
+
+      // Run code in a new namespace.
+      pyodide.runPython(e.data.code);
+    } catch (error) {
+      self.postMessage({
+        kind: "run-code-output",
+        requestID: requestID,
+        output: {type: "error", line: error.toString()},
+      });
+    } finally {
+      // Unregister stdout callback.
+      onStdout = null;
+
+      self.postMessage({
+        kind: "run-code-done",
+        requestID: requestID,
+      });
+    }
+  }
+};