Wrangler deploy fails for Python Worker with "Invalid magic number 0" error (code 10021)

[MujurID]

What versions & operating system are you using?

Wrangler 4.21.2

Please provide a link to a minimal reproduction

https://github.com/cloudflare/python-workers-examples/tree/main/01-hello

Describe the Bug

When attempting to deploy a Python Worker, specifically the 01-hello example from the cloudflare/python-workers-examples repository, the wrangler deploy command fails with an "Invalid magic number 0" error.

Steps to reproduce:

1. Ensure Wrangler 4.21.2 is installed and configured.
2. Clone the cloudflare/python-workers-examples repository: git clone https://github.com/cloudflare/python-workers-examples.git
3. Navigate into the 01-hello example directory: cd python-workers-examples/01-hello
4. Run the deployment command: wrangler deploy

Observed behaviour:
The deployment process fails, returning an API error from Cloudflare, with the following message:

X [ERROR] A request to the Cloudflare API (/accounts/[REDACTED]/workers/scripts/hello-python) failed.

  Uncaught Error: Invalid magic number 0, expected 1886286592
    at null.<anonymous> (pyodide-internal:snapshot:313:15) in decodeSnapshot
    at null.<anonymous> (pyodide-internal:snapshot:20:30)
   [code: 10021]


  If you think this is a bug, please open an issue at:
  https://github.com/cloudflare/workers-sdk/issues/new/choose

Expected behaviour:
The Python Worker should deploy successfully to Cloudflare Workers without errors, and the API request should complete as expected.

Please provide any relevant error logs

No response

[harshalmore31]

Hi @MujurID ! I’ve gone through the reproduction steps with the latest setup:

• Wrangler Version: 4.21.2
• Repo: cloudflare/python-workers-examples → 01-hello
• OS: Windows 11

Result:
After running wrangler deploy, the Python Worker deployed successfully on my end. I received the expected warnings about Python workers being experimental, but no "Invalid magic number 0" error occurred.

PS D:\cf\python-workers-examples\01-hello> wrangler deploy        
   
 ⛅️ wrangler 4.21.2
───────────────────
▲ [WARNING] The entrypoint src\entry.py defines a Python worker, support for Python workers is currently experimental. Python workers with a requirements.txt file can only be run locally and cannot be deployed.


▲ [WARNING] The module rule {"type":"Data","globs":["vendor/**/*.so"]} does not have a fallback, the following rules will be ignored:

   {"type":"Data","globs":["**/*.bin"]} (DEFAULT)

  Add `fallthrough = true` to rule to allow next rule to be used or `fallthrough = false` to silence
  this warning


▲ [WARNING] The module rule {"type":"Data","globs":["vendor/**/*.so"]} does not have a fallback, the following rules will be ignored:

   {"type":"Data","globs":["**/*.bin"]} (DEFAULT)

  Add `fallthrough = true` to rule to allow next rule to be used or `fallthrough = false` to silence
  this warning


Total Upload: 0.10 KiB / gzip: 0.11 KiB
Worker Startup Time: 2594 ms
Uploaded hello-python (8.54 sec)
Deployed hello-python triggers (3.41 sec)
  https://hello-python.harshalmore2468.workers.dev
Current Version ID: 960ce4fa-06c9-4b83-ba78-a5a389f8efd5
PS D:\cf\python-workers-examples\01-hello> 

Conclusion:
Since I'm unable to reproduce the issue, it may have been environment-specific or resolved in recent updates.
Could you try reproducing this again? If you're no longer experiencing the issue, this can likely be closed as resolved.

Thanks!

[MujurID]

I think the problem is solved, I have reproduced it and it works without any problems now.