Fixes Python print()s not showing up in wrangler dev.

src/pyodide/internal/python.ts

@@ -102,5 +102,18 @@ export async function loadPyodide(
   const pyodide = Module.API.public_api;
 
   finishSnapshotSetup(pyodide);
+
+  Module.API.initializeStreams();
+
+  // Need to set these here so that the logs go to the right context. If we don't they will go
+  // to SetupEmscripten's context and end up being KJ_LOG'd, which we do not want.
+  pyodide.setStdout({
+    batched: (msg: any) => console.log(msg),
+  });
+
+  pyodide.setStderr({
+    batched: (msg: any) => console.error(msg),
+  });
+
   return pyodide;
 }

src/pyodide/types/Pyodide.d.ts

@@ -13,4 +13,6 @@ interface Pyodide {
   FS: FS;
   site_packages: string;
   loadPackage: (names: string | string[], options: object) => Promise<any[]>;
+  setStdout: (options?: any) => void;
+  setStderr: (options?: any) => void;
 }

src/pyodide/types/emscripten.d.ts

@@ -10,11 +10,24 @@ interface PyodideConfig {
   indexURL?: string;
 }
 
+type InFuncType = () =>
+  | null
+  | undefined
+  | string
+  | ArrayBuffer
+  | Uint8Array
+  | number;
+
 interface API {
   config: PyodideConfig;
   finalizeBootstrap: () => void;
   public_api: Pyodide;
   rawRun: (code: string) => [status: number, err: string];
+  initializeStreams: (
+    stdin?: InFuncType,
+    stdout?: (a: string) => void,
+    stderr?: (a: string) => void
+  ) => void;
 }
 
 interface LDSO {

src/workerd/server/tests/python/hello/worker.py

@@ -1,4 +1,5 @@
 def test():
+    from js import console
     from js.WebAssembly import Suspending
 
     Suspending  # noqa: B018
@@ -7,3 +8,4 @@ def test():
     # because we don't test whether we printed anything.
     # TODO: update this to test that something happened
     print("Does this work?")
+    console.log("Does this work?")  # both should print the same output