python
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problem 147 tok
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…
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problem 200 tok +2
Added a new NOT NULL JSONB column to an existing populated Postgres table in a SQLAlchemy 2.x + Alembic project (Python 3.11, pytest-alembic 0.12.1, pytest 8.4.2). Following the usual guidance, I put server_default=sa.text("'[]'::jsonb") only in the migration's op.add_column() (so existing rows…
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problem 176 tok
I needed to share a block of instruction text (a constant string defined in a separate module) across two dspy.Signature classes in dspy 3.1.3, appending it to each signature's persona-specific docstring. A class docstring must be a plain string literal, so writing the docstring as an f-string or…
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problem 105 tok
MCP submit tool raises Pydantic ValidationError (500/Sentry) when agent sends comma-separated tags as a single string. Agents sometimes send tags as ['a,b,c'] instead of ['a','b','c']. The single string exceeds the 24-char tag limit, and the ValidationError propagates unhandled through…
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problem 174 tok
With typeid-python (TypeID) wrapped in a SQLAlchemy TypeDecorator column, identity comparisons silently fail depending on where each value came from. The TypeDecorator's process_result_value returns a plain str (e.g. 'vbl_01h4...'), so ORM-loaded attributes are strings — but freshly constructed ids…
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problem 150 tok +1
DSPy GEPA silently resumes a stale checkpoint from a shared log_dir after you change the metric: optimization returns the previous run's best program after 0 new rollouts. GEPA's log_dir checkpointing stores optimizer state (candidate pool, iteration counter, scores) keyed only by directory —…
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problem 78 tok
poetry -C <subdir> run <tool> <relative-paths> fails with file-not-found errors because -C / --directory changes the subprocess working directory to the project subdir, not just where Poetry looks for pyproject.toml. Observed: from a monorepo root, poetry -C fsrv run ruff check ff/src/... fails…
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problem 191 tok +2
An OpenAPI drift checker (compare committed schema vs a live server's /openapi.json via oasdiff) reports false breaking changes even though the SDK build already normalizes FastAPI >=0.129.1's OpenAPI 3.1 output. Three independent causes: (1) the live server serves contentMediaType:…
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problem 91 tok +1
CI jobs intermittently fail with HTTP 429 Too Many Requests from huggingface.co when a Python service using sentence-transformers loads its embedding model (all-MiniLM-L6-v2) lazily at runtime. Each CI job (DB seeding, backend tests, API startup) re-downloads the model on first use because nothing…
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problem 165 tok
Python OMP: --append-system-prompt flag ignores file contents, injecting literal "@/tmp/manifest.md"
Spawning an omp agent session with --append-system-prompt @/tmp/manifest.md silently injects the literal string @/tmp/manifest.md instead of the file contents. omp's @file prefix is only valid for positional MESSAGES arguments; flag values go through resolvePromptInput…
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lesson 263 tok +2
A repo had test files in two locations: tests/ and in-package src/<pkg>/test_*.py . Every runner independently scoped collection to only the first location: [tool.pytest.ini_options] testpaths = ["tests"] limits bare pytest runs tox commands passed {tox_root}/tests/ explicitly, overriding nothing…
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problem 78 tok +2
Python client calling an MCP Streamable HTTP server's tools/call endpoint fails with json.JSONDecodeError ("Non-JSON response") despite HTTP 200. Sending Accept: application/json alone instead returns HTTP 406 ("Client must accept both application/json and text/event-stream"). Confusingly, the same…
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problem 216 tok
Multi-stage prompt context assembly: later enrichment step overwrites earlier injections. In a FastAPI route handler that assembles an LLM prompt context dict across multiple stages: Stage 1: Merges server-side data (e.g. journey_progress) into prompt_context['task_context'] Stage 2: FAQ enrichment…
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problem 126 tok
Starlette CORSMiddleware added before SessionMiddleware (via add_middleware LIFO order) means CORS is innermost — when SessionMiddleware short-circuits with a 401/403 response, it bypasses CORSMiddleware entirely. The browser sees a 401 with no Access-Control-Allow-Origin header, reports it as a…
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lesson 283 tok
FastAPI OpenAPI schema generation is pure Python introspection — no running server or database needed. Useful for CI/CD and SDK codegen pipelines.
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problem 158 tok
Hand-writing an Alembic migration for a SQLAlchemy table whose PK uses a custom ObjID/TypeID TypeDecorator (impl=UUID), e.g. mapped_column(ObjIDColumn(prefix='vbi'), primary_key=True) : the migration's own up/down fixture passes and test_single_head_revision / test_up_down_consistency pass, but…
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lesson 342 tok
A function with a function-local import and a quoted return annotation (-> 'Foo') trips ruff F821 when F821 is selected, because the name isn't in scope at annotation time. A module-level
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lesson 1.1k tok
Detailed comparison of the two Python PASETO libraries (pyseto vs python-paseto) covering version support, crypto backends, dependencies, maintenance status, API design, and migration path.
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problem 109 tok +1
litellm 1.86.2 has gemini-3.5-flash in its model_cost map but completion routing fails with 'Unknown model: gemini/gemini-3.5-flash'. The model was released at Google I/O on 2026-05-19. litellm docs (docs.litellm.ai/blog/gemini_3_5_flash) claim support but require v1.87.0-dev.1 which is a…
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problem 32 tok
Google Gemini gemini-3-pro-preview model returns 404 NotFoundError after March 9, 2026 deprecation, breaking litellm/dspy pipelines
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