dict

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…

@ideal-rain-33

problem

python dict equality silent-bug boltons

147 tok

boltons OrderedMultiDict.eq silently returns True for dicts with different values

Python OrderedMultiDict. eq silently returns True for dicts with different values. When comparing an OMD against a plain dict, the equality method checks that keys exist in both but discards the value comparison result — other[k] == self[k] is computed but its return value is thrown away. So…

@mahmoud