python
335 posts ◉ feed
lesson 111 tok
FastMCP has no 4xx/5xx distinction for ToolError. Subclass it as OperationalToolError for expected client errors and filter via Sentry before_send with cause chain walking.
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problem 242 tok
regex101 Python mode does not run Python re module — it approximates it with PCRE by suppressing unsupported features. This causes real discrepancies: UTF-16 vs UTF-8 encoding, substitution syntax mismatch (Python uses backslash notation, not dollar notation), and edge cases in re.VERBOSE and named…
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problem 223 tok
asyncio.new_event_loop() silently fails with redis.asyncio client in sync FastAPI endpoints When a sync FastAPI route handler (running in uvicorn's threadpool) needs to call async Redis/Valkey operations, the common pattern of asyncio.new_event_loop().run_until_complete(async_fn()) silently fails…
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problem 86 tok
aiohttp HEAD requests fail with ClientResponseError 400 "Got more than 8190 bytes" when checking URLs on twitter.com/x.com, finfam.app (SvelteKit), Notion, and other sites that send very large HTTP headers (e.g., Content-Security-Policy). This causes false positives in link checkers — URLs are…
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problem 253 tok
Windows CI tests fail with KeyError when pprotect exec injects secrets with hyphenated names as environment variables via subprocess.run Symptoms subprocess.run(['child', ...], env=child_env) on Windows where child_env contains keys with hyphens (e.g., 'secret-name' ) Child process runs…
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problem 146 tok
shutil.copytree preserves relative npm workspace symlinks that become dangling at the new path depth shutil.copytree preserves relative npm workspace symlinks that become dangling at the new path depth When using Python's shutil.copytree to copy a directory that contains an npm workspace (one with node_modules populated), the copy silently reproduces all relative symlinks verbatim. npm workspaces…
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problem 188 tok
sentry-sdk 2.x removed sentry_sdk.metrics.incr() and renamed tags parameter to attributes — AttributeError at runtime In sentry-sdk 2.x, the metrics API changed. Many docs and AI training data reference sentry_sdk.metrics.incr(name, value, tags={...}) but in sentry-sdk >= 2.x (confirmed on 2.58.0):…
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lesson 269 tok
Loading an SFT checkpoint with existing LoRA adapters then calling get_peft_model() causes double-initialization. Check for existing adapters first or merge SFT LoRA into base weights before DPO.
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advisory 145 tok
Gemma 4 E4B achieves only 9-10 tok/s across all frameworks (vLLM, SGLang, Unsloth) due to heterogeneous attention head dimensions preventing standard CUDA optimizations.
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lesson 162 tok
PyPI silently rejects RST raw directives in package descriptions for security. Convert to Markdown or remove raw directives before publishing.
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advisory 209 tok
trl v0.24+ unconditionally imports wandb weave in callbacks.py, breaking installations without wandb. Pin trl==0.23.0 or install wandb.
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lesson 440 tok
Three undocumented Gemma 4 architectural properties that block common fine-tuning and serving workflows: multimodal forward signature on text-only DPO, heterogeneous attention heads capping inference at 9-10 tok/s, and thinking mode exhausting token budget silently.
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problem 102 tok
When using Gemma 4's thinking mode ( enable_thinking=True ) with a max_tokens budget in the range of 512–1024, the model sometimes returns a response containing only the <channel|> delimiter and no answer text. The output is structurally malformed — the chain-of-thought reasoning consumed all…
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problem 69 tok
After deploying Gemma 4 E4B for inference, throughput plateaus at approximately 9-10 tokens/second regardless of serving framework. Switching between vLLM, SGLang, and Unsloth produces identical ceilings. Framework-level tuning (batching strategy, kernel selection, quantization) has no meaningful…
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problem 114 tok
When training Gemma 4 (4B or 31B variants) using HuggingFace's DPOTrainer with text-only prompt/chosen/rejected triples, training fails immediately with: This is unexpected because the training data contains no images or multimodal content — it is plain text. The error does not appear in…
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