infochanged

Workers - Python and JavaScript Workers can now call each other via RPC

Announced: 2026-08-03
Tags: Workers
Severity: info, set by reef/rss-rule-v1
Source: https://developers.cloudflare.com/changelog/post/2026-08-03-python-javascript-rpc/

You can now call methods between Python and JavaScript Workers using <a href="https://developers.cloudflare.com/workers/runtime-apis/rpc/">Workers RPC</a>. This works through <a href="https://developers.cloudflare.com/workers/runtime-apis/bindings/service-bindings/rpc/">Service bindings</a> without extra dependencies, schema definitions, or serialization code. Cross-language RPC calls behave like ordinary function calls. Exceptions propagate to the call site. You can pass <a href="https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm#supported_types" target="_blank" rel="noopener">structured cloneable types ↗︎</a> as parameters or return values, and Pyodide Foreign Function Interface (FFI) automatically converts types between languages. <div tabindex="-1" class="heading-wrapper level-h4"><h4 id="call-a-typescript-worker-from-python">Call a TypeScript Worker from Python</h4><a class="anchor-link" href="#call-a-typescript-worker-from-python"><svg width="16" height="16" viewBox="0 0 24 24"><path fill="currentcolor" d="m12.11 15.39-3.88 3.88a2.52 2.52 0 0 1-3.5 0 2.47 2.47 0 0 1 0-3.5l3.88-3.88a1 1 0 0 0-1.42-1.42l-3.88 3.89a4.48 4.48 0 0 0 6.33 6.33l3.89-3.88a1 1 0 1 0-1.42-1.42Zm8.58-12.08a4.49 4.49 0 0 0-6.33 0l-3.89 3.88a1 1 0 0 0 1.42 1.42l3.88-3.88a2.52 2.52 0 0 1 3.5 0 2.47 2.47 0 0 1 0 3.5l-3.88 3.88a1 1 0 1 0 1.42 1.42l3.88-3.89a4.49 4.49 0 0 0 0-6.33ZM8.83 15.17a1 1 0 0 0 1.1.22 1 1 0 0 0 .32-.22l4.92-4.92a1 1 0 0 0-1.42-1.42l-4.92 4.92a1 1 0 0 0 0 1.42Z"></path></svg></a></div> Define a method in a TypeScript Worker: <div><div data-nb-tabs data-nb-sync-key="workersExamples" class><div class="relative flex border-b border-border" role="tablist" data-nb-tabs-list></div><div class="mt-3"><div role="tabpanel" data-nb-tabs-content data-nb-tab-label="JavaScript" class><figure class="nb-code-figure nb-code-figure-titled" data-nb-lang="js"><figcaption class="nb-code-title">index.jsjs</figcaption><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="js" data-nb-lang="js"><code>import { WorkerEntrypoint } from "cloudflare:workers"; export class RpcService extends WorkerEntrypoint { async add(a, b) { return a + b; } }</code></pre></figure></div><div role="tabpanel" data-nb-tabs-content data-nb-tab-label="TypeScript" class><figure class="nb-code-figure nb-code-figure-titled" data-nb-lang="ts"><figcaption class="nb-code-title">index.tsts</figcaption><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="ts" data-nb-lang="ts"><code>import { WorkerEntrypoint } from "cloudflare:workers"; export class RpcService extends WorkerEntrypoint { async add(a: number, b: number): Promise<number> { return a + b; } }</code></pre></figure></div></div></div></div> Call it from a Python Worker through a Service binding: <figure class="nb-code-figure" data-nb-lang="python"><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="python" data-nb-lang="python"><code>from workers import Response, WorkerEntrypoint class Default(WorkerEntrypoint): async def fetch(self, request): rpc = self.env.RPC result = await rpc.add(42, 144) return Response.json({"result": result})</code></pre></figure> Configure the Service binding in the Python Worker's Wrangler configuration: <div data-nb-tabs data-nb-sync-key="wranglerConfig" class><div class="relative flex border-b border-border" role="tablist" data-nb-tabs-list></div><div class="mt-3"><div role="tabpanel" data-nb-tabs-content data-nb-tab-label="wrangler.jsonc" class><figure class="nb-code-figure" data-nb-lang="jsonc"><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="jsonc" data-nb-lang="jsonc"><code>{ "services": [ { "binding": "RPC", "service": "ts-rpc-server", "entrypoint": "RpcService" } ] }</code></pre></figure></div><div role="tabpanel" data-nb-tabs-content data-nb-tab-label="wrangler.toml" class><figure class="nb-code-figure" data-nb-lang="toml"><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="toml" data-nb-lang="toml"><code>[[services]] binding = "RPC" service = "ts-rpc-server" entrypoint = "RpcService"</code></pre></figure></div></div></div><script type="module" src="https://developers.cloudflare.com/home/runner/work/cloudflare-docs/cloudflare-docs/src/components/ui/tabs/Tabs.astro?astro&type=script&index=0&lang.ts"></script> <div tabindex="-1" class="heading-wrapper level-h4"><h4 id="call-a-python-worker-from-javascript">Call a Python Worker from JavaScript</h4><a class="anchor-link" href="#call-a-python-worker-from-javascript"><svg width="16" height="16" viewBox="0 0 24 24"><path fill="currentcolor" d="m12.11 15.39-3.88 3.88a2.52 2.52 0 0 1-3.5 0 2.47 2.47 0 0 1 0-3.5l3.88-3.88a1 1 0 0 0-1.42-1.42l-3.88 3.89a4.48 4.48 0 0 0 6.33 6.33l3.89-3.88a1 1 0 1 0-1.42-1.42Zm8.58-12.08a4.49 4.49 0 0 0-6.33 0l-3.89 3.88a1 1 0 0 0 1.42 1.42l3.88-3.88a2.52 2.52 0 0 1 3.5 0 2.47 2.47 0 0 1 0 3.5l-3.88 3.88a1 1 0 1 0 1.42 1.42l3.88-3.89a4.49 4.49 0 0 0 0-6.33ZM8.83 15.17a1 1 0 0 0 1.1.22 1 1 0 0 0 .32-.22l4.92-4.92a1 1 0 0 0-1.42-1.42l-4.92 4.92a1 1 0 0 0 0 1.42Z"></path></svg></a></div> Define a method in a Python Worker: <figure class="nb-code-figure" data-nb-lang="python"><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="python" data-nb-lang="python"><code>from workers import WorkerEntrypoint class Default(WorkerEntrypoint): async def highlight_code(self, code: str, language: str) -> dict: from pygments.formatters import HtmlFormatter from pygments import highlight from pygments.lexers import get_lexer_by_name lexer = get_lexer_by_name(language, stripall=True) formatter = HtmlFormatter(linenos=True, cssclass="highlight", style="monokai") highlighted_html = highlight(code, lexer, formatter) css = formatter.get_style_defs(".highlight") return { "html": highlighted_html, "css": css }</code></pre></figure> Call it from a JavaScript Worker through a Service binding: <div><div data-nb-tabs data-nb-sync-key="workersExamples" class><div class="relative flex border-b border-border" role="tablist" data-nb-tabs-list></div><div class="mt-3"><div role="tabpanel" data-nb-tabs-content data-nb-tab-label="JavaScript" class><figure class="nb-code-figure nb-code-figure-titled" data-nb-lang="js"><figcaption class="nb-code-title">index.jsjs</figcaption><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="js" data-nb-lang="js"><code>export default { async fetch(request, env) { const rpc = env.PYTHON_RPC; const result = await rpc.highlight_code("print(42)", "python"); return Response.json(result); }, };</code></pre></figure></div><div role="tabpanel" data-nb-tabs-content data-nb-tab-label="TypeScript" class><figure class="nb-code-figure nb-code-figure-titled" data-nb-lang="ts"><figcaption class="nb-code-title">index.tsts</figcaption><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="ts" data-nb-lang="ts"><code>export default { async fetch(request, env) { const rpc = env.PYTHON_RPC; const result = await rpc.highlight_code("print(42)", "python"); return Response.json(result); }, };</code></pre></figure></div></div></div></div> Configure the Service binding in the JavaScript Worker's Wrangler configuration: <div data-nb-tabs data-nb-sync-key="wranglerConfig" class><div class="relative flex border-b border-border" role="tablist" data-nb-tabs-list></div><div class="mt-3"><div role="tabpanel" data-nb-tabs-content data-nb-tab-label="wrangler.jsonc" class><figure class="nb-code-figure" data-nb-lang="jsonc"><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="jsonc" data-nb-lang="jsonc"><code>{ "services": [ { "binding": "PYTHON_RPC", "service": "py-rpc-server" } ] }</code></pre></figure></div><div role="tabpanel" data-nb-tabs-content data-nb-tab-label="wrangler.toml" class><figure class="nb-code-figure" data-nb-lang="toml"><pre class="astro-code astro-code-themes github-light github-dark nb-shiki-c6xiwz" tabindex="0" data-language="toml" data-nb-lang="toml"><code>[[services]] binding = "PYTHON_RPC" service = "py-rpc-server"</code></pre></figure></div></div></div> For more details on the announcement, read the <a href="https://blog.cloudflare.com/python-workers-rpc/" target="_blank" rel="noopener">blog post ↗︎</a>. For more information, refer to the <a href="https://developers.cloudflare.com/workers/runtime-apis/rpc/">Workers RPC documentation</a> and the <a href="https://developers.cloudflare.com/workers/languages/python/">Python Workers overview</a>.

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