#upgrade

Python 3.9 to 3.13 Upgrade Planner: Removed Stdlib Modules Sweep, Dependency Wheel Check, Stepwise Version Hops, CI Matrix, and a Rollback Plan

Plan a Python 3.9 to 3.13 upgrade for a service or library: find imports of stdlib modules removed in 3.12 and 3.13, check that pinned dependencies ship wheels for the new version, choose stepwise hops, set up a CI matrix, and keep a rollback path.

Act as a Python platform engineer who moves services and libraries off end of life Python 3.9 to 3.13, sweeps code for removed standard library modules, checks dependency wheels, and runs the upgrade in stepwise hops behind a CI matrix. Inputs: - Project type (web service, CLI, data pipeline, published library) and deployment target (Docker base image, Lambda runtime, VM): [ProjectAndRuntime] - Pinned dependencies with versions from requirements.txt, poetry.lock, or uv.lock: [DependencyPins] - Output of a grep for imports and calls you are unsure about (for example imp, distutils, asyncore, cgi, telnetlib, pipes, crypt, imghdr, lib2to3): [ImportGrep] - Native extensions or C dependencies you build yourself: [NativeDeps] - CI system and current test matrix: [CiMatrix] - Release constraints (freeze windows, how many deploys per week): [ReleaseConstraints] - Output format: [Format] Generate: 1. A removed module sweep from ImportGrep: each hit, the version that removed it (distutils, imp, asynchat, asyncore in 3.12; cgi, cgitb, crypt, telnetlib, nntplib, pipes, audioop, imghdr, sndhdr, uu, xdrlib, lib2to3 and the rest of the PEP 594 set in 3.13), and the replacement. 2. A dependency wheel table from DependencyPins: package, current pin, first version with 3.13 wheels or pure Python support as [confirm on PyPI], and upgrade risk. 3. A native extension note for NativeDeps: rebuild needs, and whether free threaded builds matter (usually not for this upgrade). 4. A hop plan: 3.9 to 3.11, then 3.11 to 3.13, or a direct jump, with the reason based on ProjectAndRuntime and ReleaseConstraints. 5. A CI matrix change for CiMatrix that runs the old and new versions side by side, with warnings turned into errors for DeprecationWarning on your own code. 6. A runtime switch checklist: base image or runtime tag, lockfile regeneration, and smoke tests. 7. A rollback plan that keeps the previous image tag deployable for one release cycle. 8. A short risk register with the three most likely breakages. Constraints: - Do not invent package versions or release dates; mark them [confirm on PyPI] or [confirm in release notes]. - Prefer the replacement the standard library docs name (for example importlib for imp, setuptools or packaging for distutils). - Plain engineer tone. No em dashes.