python

Pruning no-op moves by event type skips actions that change state silently

jerome / 30 août 2026

My BFS solver pruned actions whose events were all ‘blocked’. One action changed hidden state while emitting exactly that: paths came out one move long.

The same escaped code fragment through both pipeline orders: unescaping first re-creates a bare < that the tag-stripping regex then swallows as markup; stripping tags first leaves the entities untouched, and a single unescape at the end yields the intact code.

Debugging

Unescape HTML entities last, or a tag-stripping regex eats your code

jerome / 30 août 2026

My HTML-to-text viewer showed code blocks truncated at every <. The stored posts were intact — unescaping entities before stripping tags did the damage.

A.merge(B) reports 100 for every percentile while B.merge(A) reports 10,000 for every percentile; the exact pooled values are p50=100, p95=10,000, p99=10,000 over 1,060,000 observations, and both orders report a wrong count.

Python

Merging reservoir samples by replaying one buffer into the other makes percentiles order-dependent

jerome / 30 août 2026

A.merge(B) reported p99=100, B.merge(A) reported p50=10,000 — both wrong. A correct merge weights each side by its true population count, not its buffer.

Android

One primitive list, rendered by Pillow and emitted as VectorDrawable paths, keeps the Play icon and the adaptive launcher icon identical

jerome / 30 août 2026

Store icon and launcher icon drifted apart because two scripts drew them. One geometry, two renderers, and a 0.48 viewport ratio fixed it.

Two processes open edits A then B on one app; the server drops A when B is created, so process 1's later read of A gets HTTP 400 'This Edit has been deleted' while process 2's read of B returns 200.

Android

Google Play’s edits.insert silently deletes the app’s previous open edit — two parallel API scripts fail with ‘This Edit has been deleted’

jerome / 30 août 2026

Two Play API clients on one app: the second edits.insert discards the first edit and every call on it returns HTTP 400. Serialize per package.

Lookup chain from a dataclass field with a string annotation through dataclasses._is_type to sys.modules: unregistered, the by-name lookup returns None and .__dict__ raises AttributeError; registered first, the same lookup finds the module and the class builds.

Python

A NoneType AttributeError inside dataclasses means your importlib-loaded module is missing from sys.modules

jerome / 18 août 2026

Loading a .py by path crashes in dataclasses._is_type when it uses future annotations. The fix: sys.modules[spec.name] = mod before exec_module.

Two writers sharing the name state.json.tmp truncate each other's file and publish 0 bytes, while mkstemp gives each writer a private name and every rename publishes a complete file.

Python

os.replace is atomic, but a shared .tmp name one step earlier still corrupts the file

jerome / 18 août 2026

Six processes writing one state file via a fixed .tmp name: 121-162 corrupt reads out of 200. tempfile.mkstemp in the same directory: zero.