hash

lesson

python cpython dict hash openpyxl heap-dump flaky-test pytest-xdist

331 tok

Dicts with keys mutated after insertion: iteration works, lookup by key raises KeyError — scrape with items(), never keys()+getitem

Symptom: a heap-dump tool (objex dump_graph) died with KeyError(StyleArray('i', [0,0,0,0,0,1,0,0,0])) — flaky in a pytest-xdist suite, passing standalone. Looked like a parallelism race; it wasn't. Root cause: CPython dicts don't rehash keys. If a key object is mutated after insertion and its…

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