Sample
six lazy moved descriptors cache resolved targets directly onto instance dictionaries while deleting themselves from parent class dictionaries, causing class-level lookups to fail and leaving sys.meta_path importers decoupled from remove_move and add_move
sha256:b632b8e946a5c728dc7d1654280ec14c45ffffd3c37cf0d43ddaa4ece84a11da
PUBLISHED
L3_CONTRACT_PASS
MIT-0
Execution evidence
Declared environment and signed verification runs are separated so you can see exactly what this sample proves.
Evidence basisSigned contract pass
Verification receipts1
Verification levelL3_CONTRACT_PASS
Declared environment
- Execution context
- python
- Operating system
- linux
- Architecture
- x64
- Runtime
- python
- Language
- python
- Package manager
- pip
Verification-run environments
- Execution context
- python 3.12
- Operating system
- linux alpine · musl
- Architecture
- x64
- Runtime
- python 3.12
- Language
- python
- Package manager
- pip
- Execution
- container · docker
CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · python@1 · 2026-08-17
Case
- Goal
- six lazy moved descriptors cache resolved targets directly onto instance dictionaries while deleting themselves from parent class dictionaries, causing class-level lookups to fail and leaving sys.meta_path importers decoupled from remove_move and add_move HOW
- Packages
-
six 1.17.0
- Environment
- python
- Created
- 2026-08-17T07:05:16Z
Commonly assumed
Accessing moved attributes on six.moves or its classes returns the descriptor or resolved object identically without mutating class state, and six.remove_move cleans up import hooks alongside attribute access
The sample's author recorded this as what a developer or model would expect here. The contract below is what actually ran.
Contract
- Accessing an attribute on six.moves or its lazy namespaces resolves the target, caches it in the instance dictionary, and deletes the lazy descriptor from the class dictionary, making class-level attribute access fail with AttributeError
- Accessing unresolved lazy descriptors directly on six._MovedItems raises AttributeError because _LazyDescr attempts setattr on None instead of returning self
- six.remove_move purges moves from _MovedItems and six.moves instance dictionaries while leaving six._importer.known_modules intact, allowing subsequent import statements to re-resolve the removed module
- six.add_move registers descriptors on _MovedItems for attribute lookup but does not update six._importer.known_modules, causing direct import statements for added moves to raise ModuleNotFoundError
- Direct attribute lookup on MovedModule instances resolves the underlying module and caches the attribute on the descriptor instance via __getattr__
- six.reraise clears its local value and traceback references in a finally block to prevent circular reference cycles between execution frames and traceback objects
Files
- NOTES.md
- csx.json
- requirements.txt
- test/__init__.py
- test/contract.py
Download the source artifact (tar.gz)
Origin Seeder
csx-seed
Verification receipts
- python 3.12 · linux alpine/x64 · docker · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · python@1 · 2026-08-17 · ed25519:d91480838ac982c9