PEP 810: Clarify sys.lazy_modules contract#4954
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johnslavik wants to merge 6 commits intopython:mainfrom
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PEP 810: Clarify sys.lazy_modules contract#4954johnslavik wants to merge 6 commits intopython:mainfrom
sys.lazy_modules contract#4954johnslavik wants to merge 6 commits intopython:mainfrom
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Clarify the public introspection contract for ``sys.lazy_modules``: it is a read-only ``frozendict[str, frozenset[str]]`` snapshot rebuilt on each access (via ``sys.__getattr__``), not a live mutable set or dict, so user code cannot mutate the import system's bookkeeping. Add a "Public introspection API" subsection alongside the existing filter API listing, and update prose to reflect the snapshot-on-access contract under "Lazy import mechanism", "Reification", and the subinterpreter note.
Prior commit added a "Public introspection API" subsection plus prose about snapshot semantics, the registry, and sys.__getattr__ rebuild behavior. That overshoots the contract: callers only need to know the type and that it is read-only. Fold the corrected type (``frozendict[str, frozenset[str]]``) into the existing first mention under "Lazy import mechanism", drop the new subsection, and remove the imprecise claim that lazy proxies are "listed in" ``sys.lazy_modules`` (the proxies live in globals; the mapping records each module's lazy imports).
Documentation build overview
714 files changed ·
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johnslavik
commented
May 4, 2026
| there are still other unreified lazy references to it). When a package is | ||
| reified and submodules in the package were also previously lazily imported, | ||
| those submodules are *not* automatically reified but they *are* added to the | ||
| When the module is reified, its fully qualified name is removed from the |
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Part of python/cpython#148587.
PEP 123: Summary of changes)