Day 02: Concept decomposition and minimal reproductions

Worked decomposition:
1. Observed output (verified):
'data' — s.strip() allocates and returns a new string without the spaces
' data ' — s still refers to the original object; nothing rebound it
'data' — only after s = s.strip() does the name refer to the new object
2. Inputs: s = ' data ' and the expectation that calling s.strip() changes s.
3. Expected (wrong) output: 'data' on the second print — the learner assumed mutation.
4. Constraint violated: strings are immutable; strip() cannot alter the object s refers to. A method call by itself never rebinds a name — only assignment (s = ...) does.
5. Names/objects/mutation/allocation: s is a name bound to one string object; strip() allocates a new string object; no mutation occurs anywhere; the original object is unchanged and becomes unreachable only after rebinding. Contrast Day 01: list.append mutated the shared object, so b and a both saw the change.
6. Minimal reproduction (the 3-line core):

s = '  data  '
   s.strip()
   print(repr(s))   # '  data  ' — call result discarded, name unchanged

Reference workflow (OFFLINE ILLUSTRATION — authored locally, not output from a real provider; it teaches the review steps but is not live agent evidence):
1. Setup: mkdir agent-task-sandbox && cd agent-task-sandbox && find . -type f → empty.
2. Agent turn 1 (illustrative): agent creates hello.py containing print("day 02") and runs it → day 02. One write, inside scope, approved.
3. Independent verification (the learner's own evidence): find . -type f → ./hello.py only; cat hello.py → print("day 02"); python3 hello.py → day 02.
4. Review verdict: checklist all-pass; verdict "accepted — artifact verified, scope respected, 1 of 3 turns used".
5. If the tool is unavailable: record "live agent portion blocked — not executed; review workflow practised on the labelled illustration". Mastery requires that honest declaration — the illustration must not be presented as a live result.

Verified observed outputs (Linux bash):
- pwd → <sandbox-parent>/fs-sandbox
- find . -type f | sort → ./notes/drafts/ideas.txt and ./notes/todo.txt
- cat notes/todo.txt → first note
- inside notes/: pwd → <sandbox-parent>/fs-sandbox/notes; ls → drafts and todo.txt
- wc -l notes/drafts/ideas.txt → 2 notes/drafts/ideas.txt
Windows orientation only (not executed): New-Item -ItemType Directory, Set-Content, Get-Content, Get-ChildItem -Recurse, $PWD.Path, cmd: mkdir, type, dir /s, %cd%.
Note pwd prints the fresh mktemp root (<sandbox-parent> above is that private root, not your shell's original directory). Optional cleanup: run the literal rm -r -- <private-root> line the block printed - it removes exactly the root this invocation created.

Worked log format (values depend on your own records):
1. Recall (unaided): "a is c → False; sys.prefix inside venv differs from sys.base_prefix; git order untracked→staged→committed→modified→staged→clean; s.strip() left s unchanged."
2. Comparison: recall matched the recorded Day 01–02 logs on three items; one mismatch found — I recalled sys.executable as "the real binary" but my log records it as the venv path inside .venv (possibly a symlink). Correction annotated.
3. Fresh transfer (unaided): predicted {'a': 1, 'b': 2} True; ran snippet → {'a': 1, 'b': 2} True. Dict assignment binds e to the same dict object, so the mutation is visible through d.
4. Schedule: re-predict the dict-identity case in 2 days unaided; if any item is missed then, rebuild its MRE and recheck in 3 days.