[Fix] The zip function in Python 3.9 does not have the strict argument

[princepride]

Purpose

Fix #19432

Test Plan

Run the command:

uv venv -p 3.9 --seed
source .venv/bin/activate
uv pip install -U vllm \
    --torch-backend=auto \
    --extra-index-url https://wheels.vllm.ai/nightly
# vllm==0.9.1rc2
vllm serve facebook/opt-125m --port 30303

curl http://localhost:30303/v1/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{"model": "facebook/opt-125m", "prompt": "Say this is a test", "temperature": 0, "max_tokens": 7}'

Test Result

Check the python version and start the server:

Execution result:

[github-actions]

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[gemini-code-assist]

Summary of Changes

Hello @princepride, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a compatibility issue with Python 3.9 by conditionally applying the strict=True argument to the zip function call. This allows the vLLM worker components to function correctly in environments running Python versions older than 3.10, specifically targeting the reported issue in Python 3.9.

Highlights

• Python Version Compatibility: Added conditional logic to handle the strict argument of the zip function, which was introduced in Python 3.10. This ensures compatibility with Python 3.9 environments.
• Code Location: The fix is applied in the _update_states method within both the GPU and TPU model runner files.

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[gemini-code-assist]

Code Review

This pull request correctly addresses the TypeError encountered with zip(..., strict=True) on Python 3.9 by introducing a version check for sys.version_info >= (3, 10). For older Python versions, zip is now called without the strict argument.

A key consideration is that the strict=True parameter in zip (for Python 3.10+) ensures that an error is raised if the zipped iterables have different lengths. By falling back to a non-strict zip for older versions, this explicit check is lost, and zip will silently truncate to the length of the shorter iterable. My main feedback is to suggest adding a manual length check in the else blocks for both modified files to maintain the original strict behavior and prevent potential silent errors if the iterable lengths are not guaranteed to be identical.

[DarkLight1337]

Thanks for fixing!

[njhill]

Thanks @princepride and sorry for introducing this incompatibility.

IMO though it would be better to just remove the strict=True for now. It's just a conservative check and not worth this amount of extra code/complexity.

[princepride]

Thanks @princepride and sorry for introducing this incompatibility.

IMO though it would be better to just remove the strict=True for now. It's just a conservative check and not worth this amount of extra code/complexity.

@DarkLight1337 What do you think of this suggestion? By the way, the unit test failed, it seems that it is not a problem with my code

[DarkLight1337]

Yeah I'm fine with removing strict=True

[gemini-code-assist]

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