Initial setup

week-01-python-internals/day-001-gil/week-01-python-internals_day-01-gil_notes.md

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+### Day 1 — GIL + CPU-bound vs I/O-bound threading
+
+#### Goals (what "done" means)
+- [ ] I can explain the GIL in 2–3 sentences and why it impacts **CPU-bound** threading more than **I/O-bound** threading.
+- [ ] I can choose between threads, processes, and asyncio for a given workload and justify it.
+- [ ] I have benchmark results (numbers) that demonstrate the above.
+
+#### Reading (mostly)
+- [ ] Read: [What Is the Python Global Interpreter Lock (GIL)? (Real Python)](https://realpython.com/python-gil/)
+  - [ ] Write 5 bullets: what the GIL is, what it is *not*, and why it exists.
+- [ ] Read: [Understanding the Python GIL (PDF)](http://www.dabeaz.com/python/UnderstandingGIL.pdf)
+  - [ ] Write 5 bullets: where threads *do* help, where they don’t, and what "switch interval" means (high level).
+- [ ] Skim (reference): [concurrent.futures — Python docs](https://docs.python.org/3/library/concurrent.futures.html)
+  - [ ] Note the difference between `ThreadPoolExecutor` vs `ProcessPoolExecutor`.
+
+#### Hands-on (benchmark + notes)
+- [ ] Create a benchmark script that compares these variants for a **CPU-bound** function:
+  - [ ] Serial (single process, no threads)
+  - [ ] `ThreadPoolExecutor`
+  - [ ] `ProcessPoolExecutor`
+- [ ] Use a **repeatable** timing method (pick one):
+  - [ ] `timeit` (preferred for small benchmarks): [timeit — Python docs](https://docs.python.org/3/library/timeit.html)
+  - [ ] or wall-clock timing with `time.perf_counter()` (fine for longer tasks)
+- [ ] Record results in a small table (example format):
+  - [ ] workload size parameters (so you can reproduce)
+  - [ ] runtime for each approach
+  - [ ] notes on CPU utilization / behavior
+- [ ] Add an **I/O-bound** comparison:
+  - [ ] Serial loop calling `time.sleep(x)`
+  - [ ] Thread pool version (expect improvement)
+- [ ] Write "Conclusions" (minimum 6 sentences):
+  - [ ] What happened for CPU-bound?
+  - [ ] What happened for I/O-bound?
+  - [ ] What I would choose in real systems and why
+
+#### Stretch (optional)
+- [ ] Skim: [PEP 703 – Making the Global Interpreter Lock Optional in CPython](https://peps.python.org/pep-0703/)
+  - [ ] Write 3 bullets: what changes, tradeoffs, and why it matters.
+
+#### Deliverables (to commit)
+- [ ] `notes.md` updated with:
+  - [ ] explanation bullets
+  - [ ] benchmark table
+  - [ ] conclusions
+- [ ] `benchmark.py` (or similar) added with instructions to run
+
+#### Suggested commits
+- [ ] `day01: add GIL notes + benchmark scaffolding`
+- [ ] `day01: record CPU vs IO benchmark results and conclusions`