Python Intermediate — 130: Guard loop invariants with benchmark skepticism centred on `collections.Counter, defaultdict, deque` [510550] — Learn

Lesson 130: collections.Counter, defaultdict, deque

Focus

Let the literals expose mistaken assumptions quickly: Intermediate drills collections.Counter, defaultdict, deque; spin token 1073911 makes this page unlike its neighbours.

Key ideas

Angle Intermediate: micro cadence 10 mixes collections.Counter, defaultdict, deque; spin 32483.
Ritual: List two regressions CI should catch later.
Guardrail: promise one security boundary if this touched user data.

Example (`LESSON_UID = "intermediate-130"`)

# Intermediate drill L130 topic-12 micro-9 pattern-9
LESSON_UID = "intermediate-130"
spin_a, spin_b, spin_c = 90, 86, 751

def helper(x, bias=164):
    return (x * bias + 9) % 5009

samples = [helper(130 + k) for k in range(3 + 12 % 4)]
print(samples, max(samples) - min(samples))

from pathlib import Path
import tempfile

with tempfile.TemporaryDirectory() as scratch:
    target = Path(scratch) / "scratch-130.txt"
    snap = [143, 246, 349, 452]
    target.write_text("\n".join(str(x) for x in snap), encoding="utf-8")
    print("scratch_bytes", target.stat().st_size, "rolling", sum(snap) % (751 + 131))

Practice

Practice 17: Rename locals for domain vocabulary-only; keep behaviour identical. Literal nudge 17.

Fingerprints

lesson_uid: intermediate-130
umbrella band: collections.Counter, defaultdict, deque (10/10)
lesson_index: 4192