gh-142527: Docs: Clarify that random.seed() discards the sign of an integer input#142483
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hauntsaninja merged 3 commits intopython:mainfrom Dec 19, 2025
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gh-142527: Docs: Clarify that random.seed() discards the sign of an integer input#142483hauntsaninja merged 3 commits intopython:mainfrom
hauntsaninja merged 3 commits intopython:mainfrom
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If *a* is an integer, the sign of *a* is discarded in the C source code. Clarify this behavior to prevent foot guns, where a common use case might naively assume that flipping the sign will produce different sequences (e.g. for a train/test split of a synthetic data generator in machine learning).
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vstinner
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needs backport to 3.13
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AA-Turner
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Indeed:
cpython/Modules/_randommodule.c
Line 321 in 4629567
The current wording is fine, though I think it could be a little shorter (see suggestion). Will leave to @rhettinger to decide.
A
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
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Thanks for the PR! (and Adam, for the edit)
It's been ten days, so I'm going to go ahead and merge
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Thanks @karpathy for the PR, and @hauntsaninja for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14. |
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…f an integer input (pythonGH-142483) If *a* is an integer, the sign of *a* is discarded in the C source code. Clarify this behavior to prevent foot guns, where a common use case might naively assume that flipping the sign will produce different sequences (e.g. for a train/test split of a synthetic data generator in machine learning). (cherry picked from commit 610aabf) Co-authored-by: Andrej <andrej.karpathy@gmail.com> Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
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…f an integer input (pythonGH-142483) If *a* is an integer, the sign of *a* is discarded in the C source code. Clarify this behavior to prevent foot guns, where a common use case might naively assume that flipping the sign will produce different sequences (e.g. for a train/test split of a synthetic data generator in machine learning). (cherry picked from commit 610aabf) Co-authored-by: Andrej <andrej.karpathy@gmail.com> Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
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GH-142970 is a backport of this pull request to the 3.14 branch. |
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GH-142971 is a backport of this pull request to the 3.13 branch. |
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…of an integer input (GH-142483) (#142970) gh-142527: Docs: Clarify that random.seed() discards the sign of an integer input (GH-142483) If *a* is an integer, the sign of *a* is discarded in the C source code. Clarify this behavior to prevent foot guns, where a common use case might naively assume that flipping the sign will produce different sequences (e.g. for a train/test split of a synthetic data generator in machine learning). (cherry picked from commit 610aabf) Co-authored-by: Andrej <andrej.karpathy@gmail.com> Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
hauntsaninja
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…of an integer input (GH-142483) (#142971) gh-142527: Docs: Clarify that random.seed() discards the sign of an integer input (GH-142483) If *a* is an integer, the sign of *a* is discarded in the C source code. Clarify this behavior to prevent foot guns, where a common use case might naively assume that flipping the sign will produce different sequences (e.g. for a train/test split of a synthetic data generator in machine learning). (cherry picked from commit 610aabf) Co-authored-by: Andrej <andrej.karpathy@gmail.com> Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
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…f an integer input (python#142483) If *a* is an integer, the sign of *a* is discarded in the C source code. Clarify this behavior to prevent foot guns, where a common use case might naively assume that flipping the sign will produce different sequences (e.g. for a train/test split of a synthetic data generator in machine learning). Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
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If a is an integer, the sign of a is discarded in the C source code. Clarify this behavior to prevent foot guns, where a common use case might naively assume that flipping the sign will produce different sequences (e.g. for a train/test split of a synthetic data generator in machine learning).
A bit more context appears in this tweet, where I was surprised by this behavior, which led to a subtle bug that caused the train and test splits to be identical in a synthetic data generation task.
📚 Documentation preview 📚: https://cpython-previews--142483.org.readthedocs.build/