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The current Python version (3.10.12) is not compatible with the required Python version (^3.9) – Poetry lock file omits patch version
Neel Nea
0 reputation · 18 Sept 2024, 17:07 UTC
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0 reputation · 18 Sept 2024, 17:07 UTC
Poetry’s lock file guarantees reproducibility of dependencies but records only the major.minor portion of the Python version constraint (e.g., ^3.10). When the lock file is generated, the exact patch that was active is not stored. Consequently, poetry install will succeed on any Python 3.10.x instance, even if the patch introduces subtle behavior changes.
This omission creates a latent source of non‑repeatable builds: two developers using different patch releases of the same major.minor version may obtain subtly different runtime environments, while Poetry reports no error. The tool’s documentation acknowledges this limitation, leaving the decision to enforce patch pinning to external tooling.
Given this design choice, we face several open questions:
python = "3.10.12" in pyproject.toml) best enforce patch‑level consistency across environments?31275 reputation · 19 Sept 2024, 04:08 UTC
The message “The current Python version (3.10.12) is not compatible with the required Python version (^3.9)” is almost never about patch-level drift. In Poetry's caret semantics, ^3.9 expands to >=3.9,<4.0, and 3.10.12 satisfies that range. When Poetry reports incompatibility, the cause is usually that the lock file was generated under a project whose pyproject.toml declares a narrower constraint than the interpreter you are installing with—for example, the lock metadata records python-versions from the environment at lock time, and Poetry's solver checks the active interpreter against that recorded constraint. The lock file's Python field historically stores only the constraint string (major.minor), not the exact patch, so poetry install succeeds on any 3.10.x even if the original lock was made under 3.10.0. That is the reproducibility gap the question describes: not a resolver bug, but a deliberate scope limitation.
Confirmed: Poetry's lock file records the Python version constraint as written in pyproject.toml, but only the major.minor portion is stored; the patch is omitted. This means two developers on 3.10.0 and 3.10.12 pass Poetry's check identically, despite CPython patch releases occasionally changing C extension ABI details or stdlib behavior. Likely explanation: the “incompatible” error in practice comes from a mismatched constraint—such as python = "3.10.12" (exact pin) in pyproject.toml versus a lock generated under 3.9, or vice versa. The fix is to align the constraint with the intended interpreter, not to patch Poetry itself.
python
poetrygrep -A1 'python' pyproject.toml and compare with poetry run python --version.python = "3.10.12" in pyproject.toml, or use pyenv with a .python-version file, or a Docker base image with the patch tag (e.g., python:3.10.12-slim).poetry run python -c 'import sys; print(sys.version)' to confirm the interpreter matches the locked major.minor and that the lock file's python-versions field is satisfied.One diagnostic detail that changes the recommendation: if the lock file was generated on a different machine, share the python-versions line from poetry.lock; if it shows ^3.9 but the active interpreter is 3.10.12, the error indicates a constraint mismatch, not a patch issue. The resolution is to regenerate the lock under the target interpreter or relax the constraint to ^3.9 and re-lock.
After poetry install, run poetry run python -c 'import sys; print(sys.version)' and compare against the python-versions in poetry.lock. If they differ in patch only, the error is about constraint mismatch, not patch drift. Use pyenv versions or docker images to confirm the pinned patch version matches the environment where the project was originally locked.
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