# Profiling web-edit with Python 3.15: flame graphs and source heatmaps — retained record

> Retained news record from news:feed-3733c65b9abe07b4.

Canonical: https://highsignal.app/data/records/5ef59227fc1ecf7a

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source: [news](https://highsignal.app/data/news) (news:feed-3733c65b9abe07b4)  published 2026-10-12 16:58 ingested 2026-10-24 10:07

[original source ↗](https://simonwillison.net/2026/Oct/12/python-3-15-web-edit-profiling/)

## retained text



```
12th October 2026
    
      Research
    
    Profiling web-edit with Python 3.15: flame graphs and source heatmaps
    — Profiling the unmodified web-edit app with Python 3.15’s built-in `profiling.sampling` revealed that mixed line-ending preservation dominated a busy editing workload: `preserve_endings` appeared in 64.8% of 15,296 recorded CPU stacks, with `SequenceMatcher.find_longest_match` contributing 38.3% of leaf samples. Sampling all threads was essential, since 95.1% of stacks came from AnyIO’s worker thread and would have been missed by a main-thread-only profile.
  
I put the new Python 3.15 profiler through its paces by having GPT-6 Astra Extra High in Codex run it against my new web-edit app:
I need a Python 3.15 flame graph and heatmap demo of the "web-edit" app from PyPI - research first then make me those demos
Here's the resulting example flame graph and heatmap.
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```



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