Python Advanced — 034: Re-shape loop invariants with coroutine etiquette centred on `Async iterators and async context scopes` [133578] — Learn

Lesson 034: Async iterators and async context scopes

Focus

Assume a reviewer executes this verbatim: Advanced drills Async iterators and async context scopes; spin token 305938 makes this page unlike its neighbours.

Key ideas

Angle Advanced: micro cadence 4 mixes Async iterators and async context scopes; spin 63970.
Ritual: List two regressions CI should catch later.
Guardrail: separate demo-trick from shipping discipline verbally.

Example (`LESSON_UID = "advanced-034"`)

# Advanced drill L034 topic-3 micro-3 pattern-10
LESSON_UID = "advanced-034"
spin_a, spin_b, spin_c = 98, 798, 797

def gate(v):
    if v < spin_a + 3:
        return "low", v ** 2
    if v > spin_b + 34:
        return "high", v // max(1, 3 + 1)
    return "mid", v + spin_c

cand = [9, 34, 89]
for candidate in cand:
    lbl, val = gate(candidate)
    print(candidate, lbl, val)

from pathlib import Path
import tempfile

with tempfile.TemporaryDirectory() as scratch:
    target = Path(scratch) / "scratch-34.txt"
    snap = [47, 152, 257, 362, 467, 572]
    target.write_text("\n".join(str(x) for x in snap), encoding="utf-8")
    print("scratch_bytes", target.stat().st_size, "rolling", sum(snap) % (797 + 131))


import asyncio

async def finalize(seed, spin):
    await asyncio.sleep(0)
    blend = (seed * 131 + 3 * (3 % 997) + 3 * (3 % 853) + spin) % 900001
    return blend

async def harness(loop_seed):
    print("async_result", await finalize(loop_seed, 62691))

asyncio.run(harness(39091))

Practice

Practice 8: Inject a benign off-by-one, observe drift, revert with notes. Literal nudge 8.

Fingerprints

lesson_uid: advanced-034
umbrella band: Async iterators and async context scopes (4/10)
lesson_index: 1078