Implements the start of an SDK for Python Workers.

src/pyodide/internal/workers.py

@@ -0,0 +1,62 @@
+# This module defines a Workers API for Python. It is similar to the API provided by
+# JS Workers, but with changes and additions to be more idiomatic to the Python
+# programming language.
+from http import HTTPMethod, HTTPStatus
+from typing import TypedDict, Unpack
+
+import js
+
+from pyodide.http import FetchResponse, pyfetch
+
+JSBody = (
+    "js.Blob | js.ArrayBuffer | js.TypedArray | js.DataView | js.FormData |"
+    "js.ReadableStream | js.URLSearchParams"
+)
+Body = "str | JSBody"
+Headers = dict[str, str] | list[tuple[str, str]]
+
+
+class FetchKwargs(TypedDict, total=False):
+    headers: Headers | None
+    body: "Body | None"
+    method: HTTPMethod = HTTPMethod.GET
+
+
+async def fetch(
+    resource: str,
+    **other_options: Unpack[FetchKwargs],
+) -> FetchResponse:
+    if "method" in other_options and isinstance(other_options["method"], HTTPMethod):
+        other_options["method"] = other_options["method"].value
+    return await pyfetch(resource, **other_options)
+
+
+def Response(
+    body: Body,
+    status: HTTPStatus | int = HTTPStatus.OK,
+    statusText="",
+    headers: Headers = None,
+) -> js.Response:
+    """
+    Represents the response to a request.
+
+    Based on the JS API of the same name:
+    https://developer.mozilla.org/en-US/docs/Web/API/Response/Response.
+    """
+    options = {
+        "status": status.value if isinstance(status, HTTPStatus) else status,
+    }
+    if len(statusText) > 0:
+        options["statusText"] = statusText
+    if headers:
+        if isinstance(headers, list):
+            # We should have a list[tuple[str, str]]
+            options["headers"] = js.Headers.new(headers)
+        elif isinstance(headers, dict):
+            options["headers"] = js.Headers.new(headers.items())
+        else:
+            raise AssertionError(
+                "Response() received unexpected type for headers argument"
+            )
+
+    return js.Response.new(body, **options)

src/pyodide/python-entrypoint-helper.ts

@@ -93,6 +93,11 @@ export async function setupPackages(pyodide: Pyodide): Promise<void> {
     const pymajor = pyodide._module._py_version_major();
     const pyminor = pyodide._module._py_version_minor();
     pyodide.site_packages = `/lib/python${pymajor}.${pyminor}/site-packages`;
+
+    // Inject modules that enable JS features to be used idiomatically from Python.
+    pyodide.FS.mkdir(`${pyodide.site_packages}/cloudflare`);
+    await injectSitePackagesModule(pyodide, 'workers', 'cloudflare/workers');
+
     // Install patches as needed
     if (TRANSITIVE_REQUIREMENTS.has('aiohttp')) {
       await applyPatch(pyodide, 'aiohttp');
@@ -142,9 +147,17 @@ function makeHandler(pyHandlerName: string): Handler {
         'prep_python',
         async () => await preparePython()
       );
-      return await enterJaegerSpan('python_code', () => {
+
+      const result = await enterJaegerSpan('python_code', () => {
         return mainModule[pyHandlerName].callRelaxed(...args);
       });
+
+      // Support returning a pyodide.ffi.FetchResponse.
+      if (result.js_response !== undefined) {
+        return result.js_response;
+      } else {
+        return result;
+      }
     } catch (e) {
       console.warn('Error in makeHandler');
       reportError(e);