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Python Software Foundation Rule

Bundled library copies depend on build configuration

Catalog row in Vendor License Rules · Cited

Kind
Counting
Statement
History and License: the pyexpat, _ctypes and _decimal extensions are built from included copies of expat, libffi and libmpdec unless the build is configured to use the system library (--with-system-expat, --with-system-libffi, --with-system-libmpdec); zlib is included only if the system version is too old. Which third-party code (and which notices) a given Python binary contains therefore depends on how it was built, and an SBOM or build record is needed to know. (page undated; as published on 2026-09-27)
Applies when
Inventorying the third-party components inside a specific Python build (vendor, distribution or in-house).
Applies to
CPython builds from source.
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